HBASE-8024 Make Store flush algorithm pluggable

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.95@1475871 13f79535-47bb-0310-9956-ffa450edef68
HBASE-5930. Limits the amount of time an edit can live in the memstore.

git-svn-id: https://svn.apache.org/repos/asf/hbase/branches/0.95@1475874 13f79535-47bb-0310-9956-ffa450edef68
Merge remote branch 'origin/0.95' into 0.95-gd