Improve wording of new documentation section on encryption, and move it a few sections up.
Improve wording of new documentation section on encryption, and move it
a few sections up.

rvs/gpdb,Quikling/gpdb,janebeckman/gpdb,0x0FFF/gpdb,CraigHarris/gpdb,zaksoup/gpdb,zaksoup/gpdb,tangp3/gpdb,lisakowen/gpdb,edespino/gpdb,atris/gpdb,cjcjameson/gpdb,janebeckman/gpdb,arcivanov/postgres-xl,lpetrov-pivotal/gpdb,ashwinstar/gpdb,lintzc/gpdb,cjcjameson/gpdb,ahachete/gpdb,royc1/gpdb,tangp3/gpdb,Postgres-XL/Postgres-XL,lintzc/gpdb,kmjungersen/PostgresXL,royc1/gpdb,Postgres-XL/Postgres-XL,Chibin/gpdb,yazun/postgres-xl,ashwinstar/gpdb,cjcjameson/gpdb,tangp3/gpdb,50wu/gpdb,0x0FFF/gpdb,rvs/gpdb,adam8157/gpdb,adam8157/gpdb,atris/gpdb,Postgres-XL/Postgres-XL,lisakowen/gpdb,postmind-net/postgres-xl,adam8157/gpdb,xinzweb/gpdb,ashwinstar/gpdb,Chibin/gpdb,atris/gpdb,tpostgres-projects/tPostgres,chrishajas/gpdb,xuegang/gpdb,xuegang/gpdb,atris/gpdb,rvs/gpdb,adam8157/gpdb,kaknikhil/gpdb,jmcatamney/gpdb,janebeckman/gpdb,edespino/gpdb,chrishajas/gpdb,techdragon/Postgres-XL,atris/gpdb,lpetrov-pivotal/gpdb,ahachete/gpdb,xinzweb/gpdb,randomtask1155/gpdb,kaknikhil/gpdb,0x0FFF/gpdb,chrishajas/gpdb,rubikloud/gpdb,jmcatamney/gpdb,lpetrov-pivotal/gpdb,pavanvd/postgres-xl,tangp3/gpdb,royc1/gpdb,snaga/postgres-xl,zaksoup/gpdb,Quikling/gpdb,kmjungersen/PostgresXL,randomtask1155/gpdb,lintzc/gpdb,Chibin/gpdb,pavanvd/postgres-xl,cjcjameson/gpdb,lintzc/gpdb,atris/gpdb,foyzur/gpdb,postmind-net/postgres-xl,postmind-net/postgres-xl,rubikloud/gpdb,xinzweb/gpdb,ovr/postgres-xl,yuanzhao/gpdb,kmjungersen/PostgresXL,Postgres-XL/Postgres-XL,CraigHarris/gpdb,Chibin/gpdb,pavanvd/postgres-xl,xinzweb/gpdb,zeroae/postgres-xl,arcivanov/postgres-xl,lisakowen/gpdb,xuegang/gpdb,rubikloud/gpdb,arcivanov/postgres-xl,kaknikhil/gpdb,kmjungersen/PostgresXL,0x0FFF/gpdb,janebeckman/gpdb,Quikling/gpdb,foyzur/gpdb,arcivanov/postgres-xl,zaksoup/gpdb,ovr/postgres-xl,lintzc/gpdb,greenplum-db/gpdb,jmcatamney/gpdb,0x0FFF/gpdb,CraigHarris/gpdb,greenplum-db/gpdb,50wu/gpdb,oberstet/postgres-xl,50wu/gpdb,cjcjameson/gpdb,Chibin/gpdb,snaga/postgres-xl,jmcatamney/gpdb,janebeckman/gpdb,lisakowen/gpdb,royc1/gpdb,xuegang/gpdb,ahachete/gpdb,xuegang/gpdb,kaknikhil/gpdb,lpetrov-pivotal/gpdb,kaknikhil/gpdb,lisakowen/gpdb,oberstet/postgres-xl,edespino/gpdb,greenplum-db/gpdb,foyzur/gpdb,Chibin/gpdb,edespino/gpdb,xuegang/gpdb,yuanzhao/gpdb,pavanvd/postgres-xl,lpetrov-pivotal/gpdb,postmind-net/postgres-xl,zaksoup/gpdb,edespino/gpdb,snaga/postgres-xl,edespino/gpdb,edespino/gpdb,cjcjameson/gpdb,janebeckman/gpdb,zeroae/postgres-xl,yuanzhao/gpdb,50wu/gpdb,adam8157/gpdb,tangp3/gpdb,lpetrov-pivotal/gpdb,janebeckman/gpdb,tpostgres-projects/tPostgres,edespino/gpdb,postmind-net/postgres-xl,rubikloud/gpdb,adam8157/gpdb,Chibin/gpdb,ashwinstar/gpdb,50wu/gpdb,Quikling/gpdb,royc1/gpdb,ahachete/gpdb,Chibin/gpdb,kaknikhil/gpdb,janebeckman/gpdb,atris/gpdb,chrishajas/gpdb,50wu/gpdb,yazun/postgres-xl,techdragon/Postgres-XL,foyzur/gpdb,ashwinstar/gpdb,randomtask1155/gpdb,lisakowen/gpdb,lisakowen/gpdb,Postgres-XL/Postgres-XL,randomtask1155/gpdb,lintzc/gpdb,tangp3/gpdb,kaknikhil/gpdb,jmcatamney/gpdb,janebeckman/gpdb,yuanzhao/gpdb,oberstet/postgres-xl,ovr/postgres-xl,jmcatamney/gpdb,adam8157/gpdb,tangp3/gpdb,chrishajas/gpdb,ashwinstar/gpdb,rvs/gpdb,xinzweb/gpdb,Quikling/gpdb,lintzc/gpdb,Quikling/gpdb,greenplum-db/gpdb,yuanzhao/gpdb,jmcatamney/gpdb,atris/gpdb,50wu/gpdb,ovr/postgres-xl,randomtask1155/gpdb,rubikloud/gpdb,arcivanov/postgres-xl,kmjungersen/PostgresXL,CraigHarris/gpdb,royc1/gpdb,lintzc/gpdb,yazun/postgres-xl,yuanzhao/gpdb,ashwinstar/gpdb,foyzur/gpdb,randomtask1155/gpdb,oberstet/postgres-xl,royc1/gpdb,edespino/gpdb,rvs/gpdb,Quikling/gpdb,foyzur/gpdb,ovr/postgres-xl,rvs/gpdb,Chibin/gpdb,techdragon/Postgres-XL,snaga/postgres-xl,rvs/gpdb,tpostgres-projects/tPostgres,xinzweb/gpdb,Quikling/gpdb,xuegang/gpdb,ahachete/gpdb,lisakowen/gpdb,pavanvd/postgres-xl,oberstet/postgres-xl,edespino/gpdb,lpetrov-pivotal/gpdb,xinzweb/gpdb,rubikloud/gpdb,ahachete/gpdb,greenplum-db/gpdb,rvs/gpdb,snaga/postgres-xl,CraigHarris/gpdb,royc1/gpdb,yuanzhao/gpdb,adam8157/gpdb,yazun/postgres-xl,yazun/postgres-xl,Quikling/gpdb,ashwinstar/gpdb,kaknikhil/gpdb,zaksoup/gpdb,rvs/gpdb,randomtask1155/gpdb,CraigHarris/gpdb,jmcatamney/gpdb,Chibin/gpdb,rvs/gpdb,kaknikhil/gpdb,greenplum-db/gpdb,ahachete/gpdb,greenplum-db/gpdb,cjcjameson/gpdb,janebeckman/gpdb,xuegang/gpdb,xuegang/gpdb,cjcjameson/gpdb,chrishajas/gpdb,0x0FFF/gpdb,yuanzhao/gpdb,zeroae/postgres-xl,ahachete/gpdb,techdragon/Postgres-XL,tpostgres-projects/tPostgres,tangp3/gpdb,50wu/gpdb,rubikloud/gpdb,arcivanov/postgres-xl,zaksoup/gpdb,lpetrov-pivotal/gpdb,randomtask1155/gpdb,CraigHarris/gpdb,cjcjameson/gpdb,chrishajas/gpdb,Quikling/gpdb,0x0FFF/gpdb,techdragon/Postgres-XL,rubikloud/gpdb,tpostgres-projects/tPostgres,zeroae/postgres-xl,chrishajas/gpdb,CraigHarris/gpdb,yuanzhao/gpdb,cjcjameson/gpdb,foyzur/gpdb,xinzweb/gpdb,0x0FFF/gpdb,yuanzhao/gpdb,CraigHarris/gpdb,foyzur/gpdb,zaksoup/gpdb,zeroae/postgres-xl,kaknikhil/gpdb,lintzc/gpdb,greenplum-db/gpdb