Add Apache License section to Readme.
Add Apache License section to Readme.

jankotek/mapdb,pettermahlen/mapdb,cocosli/mapdb,jankotek/mapdb,sumit784/mapdb,SleimanJneidi/mapdb,ffjiao/mapdb,mebigfatguy/mapdb,ringoluo/mapdb,jankotek/MapDB,hangum/mapdb,codeaudit/mapdb,morfeo8marc/mapdb,olupas/MapDB,lamfire/mapdb,mebigfatguy/mapdb,olupas/MapDB,binarytemple/mapdb,jankotek/MapDB