[Java] Improve the Java Doc of RocksObject
[Java] Improve the Java Doc of RocksObject

Summary:
Improve the Java Doc of RocksObject, which explains more about the life-cycle
of a native handle.

Test Plan: no code change

Reviewers: haobo, sdong, ankgup87

Reviewed By: ankgup87

Subscribers: leveldb

Differential Revision: https://reviews.facebook.net/D19179

JoeWoo/rocksdb,biddyweb/rocksdb,tizzybec/rocksdb,RyanTech/rocksdb,tschottdorf/rocksdb,dkorolev/rocksdb,OverlordQ/rocksdb,JackLian/rocksdb,sorphi/rocksdb,caijieming-baidu/rocksdb,ylong/rocksdb,lgscofield/rocksdb,JohnPJenkins/rocksdb,skunkwerks/rocksdb,caijieming-baidu/rocksdb,JackLian/rocksdb,vashstorm/rocksdb,caijieming-baidu/rocksdb,JackLian/rocksdb,Andymic/rocksdb,zhangpng/rocksdb,dkorolev/rocksdb,OverlordQ/rocksdb,luckywhu/rocksdb,Andymic/rocksdb,vashstorm/rocksdb,fengshao0907/rocksdb,RyanTech/rocksdb,wskplho/rocksdb,bbiao/rocksdb,ylong/rocksdb,wat-ze-hex/rocksdb,siddhartharay007/rocksdb,bbiao/rocksdb,vmx/rocksdb,JoeWoo/rocksdb,tsheasha/rocksdb,facebook/rocksdb,biddyweb/rocksdb,tsheasha/rocksdb,skunkwerks/rocksdb,hobinyoon/rocksdb,vmx/rocksdb,NickCis/rocksdb,makelivedotnet/rocksdb,luckywhu/rocksdb,flabby/rocksdb,OverlordQ/rocksdb,wlqGit/rocksdb,siddhartharay007/rocksdb,wlqGit/rocksdb,kaschaeffer/rocksdb,wat-ze-hex/rocksdb,tizzybec/rocksdb,JohnPJenkins/rocksdb,JohnPJenkins/rocksdb,virtdb/rocksdb,flabby/rocksdb,wat-ze-hex/rocksdb,virtdb/rocksdb,tizzybec/rocksdb,vmx/rocksdb,ylong/rocksdb,hobinyoon/rocksdb,jalexanderqed/rocksdb,mbarbon/rocksdb,rDSN-Projects/rocksdb.replicated,vashstorm/rocksdb,wenduo/rocksdb,jalexanderqed/rocksdb,makelivedotnet/rocksdb,caijieming-baidu/rocksdb,wskplho/rocksdb,wskplho/rocksdb,JohnPJenkins/rocksdb,norton/rocksdb,mbarbon/rocksdb,makelivedotnet/rocksdb,anagav/rocksdb,sorphi/rocksdb,ryneli/rocksdb,sorphi/rocksdb,skunkwerks/rocksdb,anagav/rocksdb,kaschaeffer/rocksdb,makelivedotnet/rocksdb,caijieming-baidu/rocksdb,Vaisman/rocksdb,norton/rocksdb,ryneli/rocksdb,norton/rocksdb,bbiao/rocksdb,ylong/rocksdb,wlqGit/rocksdb,jalexanderqed/rocksdb,jalexanderqed/rocksdb,tschottdorf/rocksdb,ylong/rocksdb,mbarbon/rocksdb,virtdb/rocksdb,virtdb/rocksdb,norton/rocksdb,kaschaeffer/rocksdb,zhangpng/rocksdb,msb-at-yahoo/rocksdb,facebook/rocksdb,geraldoandradee/rocksdb,amyvmiwei/rocksdb,alihalabyah/rocksdb,ryneli/rocksdb,tsheasha/rocksdb,Applied-Duality/rocksdb,ylong/rocksdb,wenduo/rocksdb,siddhartharay007/rocksdb,SunguckLee/RocksDB,JoeWoo/rocksdb,SunguckLee/RocksDB,wskplho/rocksdb,amyvmiwei/rocksdb,tsheasha/rocksdb,Andymic/rocksdb,wat-ze-hex/rocksdb,anagav/rocksdb,lgscofield/rocksdb,msb-at-yahoo/rocksdb,temicai/rocksdb,luckywhu/rocksdb,norton/rocksdb,fengshao0907/rocksdb,NickCis/rocksdb,temicai/rocksdb,vmx/rocksdb,hobinyoon/rocksdb,facebook/rocksdb,kaschaeffer/rocksdb,fengshao0907/rocksdb,JoeWoo/rocksdb,rDSN-Projects/rocksdb.replicated,SunguckLee/RocksDB,RyanTech/rocksdb,wlqGit/rocksdb,Vaisman/rocksdb,NickCis/rocksdb,rDSN-Projects/rocksdb.replicated,tsheasha/rocksdb,bbiao/rocksdb,RyanTech/rocksdb,dkorolev/rocksdb,wenduo/rocksdb,SunguckLee/RocksDB,lgscofield/rocksdb,alihalabyah/rocksdb,siddhartharay007/rocksdb,jalexanderqed/rocksdb,alihalabyah/rocksdb,Applied-Duality/rocksdb,ryneli/rocksdb,Applied-Duality/rocksdb,wat-ze-hex/rocksdb,geraldoandradee/rocksdb,geraldoandradee/rocksdb,kaschaeffer/rocksdb,hobinyoon/rocksdb,wenduo/rocksdb,hobinyoon/rocksdb,tsheasha/rocksdb,JackLian/rocksdb,wenduo/rocksdb,msb-at-yahoo/rocksdb,wskplho/rocksdb,skunkwerks/rocksdb,biddyweb/rocksdb,makelivedotnet/rocksdb,skunkwerks/rocksdb,mbarbon/rocksdb,biddyweb/rocksdb,ryneli/rocksdb,hobinyoon/rocksdb,fengshao0907/rocksdb,ryneli/rocksdb,caijieming-baidu/rocksdb,makelivedotnet/rocksdb,hobinyoon/rocksdb,wenduo/rocksdb,wat-ze-hex/rocksdb,luckywhu/rocksdb,dkorolev/rocksdb,rDSN-Projects/rocksdb.replicated,wskplho/rocksdb,IMCG/RcoksDB,SunguckLee/RocksDB,sorphi/rocksdb,Applied-Duality/rocksdb,wenduo/rocksdb,siddhartharay007/rocksdb,alihalabyah/rocksdb,JohnPJenkins/rocksdb,lgscofield/rocksdb,tschottdorf/rocksdb,vmx/rocksdb,SunguckLee/RocksDB,Applied-Duality/rocksdb,vashstorm/rocksdb,biddyweb/rocksdb,IMCG/RcoksDB,jalexanderqed/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,luckywhu/rocksdb,tschottdorf/rocksdb,tschottdorf/rocksdb,NickCis/rocksdb,facebook/rocksdb,lgscofield/rocksdb,Vaisman/rocksdb,Applied-Duality/rocksdb,rDSN-Projects/rocksdb.replicated,Andymic/rocksdb,bbiao/rocksdb,msb-at-yahoo/rocksdb,OverlordQ/rocksdb,dkorolev/rocksdb,OverlordQ/rocksdb,Vaisman/rocksdb,Andymic/rocksdb,JohnPJenkins/rocksdb,tschottdorf/rocksdb,JackLian/rocksdb,lgscofield/rocksdb,alihalabyah/rocksdb,geraldoandradee/rocksdb,alihalabyah/rocksdb,IMCG/RcoksDB,mbarbon/rocksdb,lgscofield/rocksdb,Andymic/rocksdb,amyvmiwei/rocksdb,temicai/rocksdb,siddhartharay007/rocksdb,Vaisman/rocksdb,biddyweb/rocksdb,jalexanderqed/rocksdb,zhangpng/rocksdb,ryneli/rocksdb,zhangpng/rocksdb,JackLian/rocksdb,tsheasha/rocksdb,vmx/rocksdb,tizzybec/rocksdb,IMCG/RcoksDB,skunkwerks/rocksdb,msb-at-yahoo/rocksdb,norton/rocksdb,JohnPJenkins/rocksdb,fengshao0907/rocksdb,bbiao/rocksdb,temicai/rocksdb,amyvmiwei/rocksdb,vashstorm/rocksdb,vmx/rocksdb,flabby/rocksdb,Andymic/rocksdb,luckywhu/rocksdb,sorphi/rocksdb,fengshao0907/rocksdb,JoeWoo/rocksdb,facebook/rocksdb,vashstorm/rocksdb,alihalabyah/rocksdb,IMCG/RcoksDB,facebook/rocksdb,tsheasha/rocksdb,virtdb/rocksdb,SunguckLee/RocksDB,wlqGit/rocksdb,zhangpng/rocksdb,luckywhu/rocksdb,facebook/rocksdb,bbiao/rocksdb,geraldoandradee/rocksdb,virtdb/rocksdb,hobinyoon/rocksdb,flabby/rocksdb,mbarbon/rocksdb,siddhartharay007/rocksdb,norton/rocksdb,dkorolev/rocksdb,mbarbon/rocksdb,temicai/rocksdb,NickCis/rocksdb,sorphi/rocksdb,zhangpng/rocksdb,JoeWoo/rocksdb,sorphi/rocksdb,rDSN-Projects/rocksdb.replicated,biddyweb/rocksdb,zhangpng/rocksdb,JackLian/rocksdb,wlqGit/rocksdb,RyanTech/rocksdb,vmx/rocksdb,wlqGit/rocksdb,wskplho/rocksdb,rDSN-Projects/rocksdb.replicated,RyanTech/rocksdb,fengshao0907/rocksdb,temicai/rocksdb,tizzybec/rocksdb,anagav/rocksdb,OverlordQ/rocksdb,tizzybec/rocksdb,wenduo/rocksdb,anagav/rocksdb,wat-ze-hex/rocksdb,IMCG/RcoksDB,NickCis/rocksdb,RyanTech/rocksdb,OverlordQ/rocksdb,Vaisman/rocksdb,flabby/rocksdb,geraldoandradee/rocksdb,facebook/rocksdb,dkorolev/rocksdb,IMCG/RcoksDB,anagav/rocksdb,kaschaeffer/rocksdb,tizzybec/rocksdb,amyvmiwei/rocksdb,makelivedotnet/rocksdb,ylong/rocksdb,vashstorm/rocksdb,skunkwerks/rocksdb,virtdb/rocksdb,flabby/rocksdb,amyvmiwei/rocksdb,wat-ze-hex/rocksdb,kaschaeffer/rocksdb,caijieming-baidu/rocksdb,norton/rocksdb,NickCis/rocksdb,flabby/rocksdb,JoeWoo/rocksdb,Vaisman/rocksdb,anagav/rocksdb,Applied-Duality/rocksdb,Andymic/rocksdb,temicai/rocksdb,geraldoandradee/rocksdb,amyvmiwei/rocksdb,msb-at-yahoo/rocksdb