HBASE-7784 move the code related to compaction selection specific to default compaction policy, into default compaction policy (from HStore) (Sergey)



git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1444298 13f79535-47bb-0310-9956-ffa450edef68
STEP 1 - Isolate fs related code to HRegionFileSystem
STEP 2 - Refactor HStore to use HRegionFileSystem
test fix