HBASE-7809 Refactor Split/Merge to use HRegionFileSystem

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1457148 13f79535-47bb-0310-9956-ffa450edef68
REVERT HBASE-8034 record on-disk data size for store file and make it available during writing

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1457193 13f79535-47bb-0310-9956-ffa450edef68