ACCUMULO-2041 extract tablet classes to new files, move tablet-related code to o.a.a.tserver.tablet, make member variables private
ACCUMULO-2041 updates from initial review
ACCUMULO-2041 more review updates
ACCUMULO-2766 fix wal group commit
Merge branch '1.5.2-SNAPSHOT' into 1.6.1-SNAPSHOT

Conflicts:
	server/tserver/src/main/java/org/apache/accumulo/tserver/log/DfsLogger.java
Merge branch '1.6.1-SNAPSHOT'
ACCUMULO-2041 provide alternative name for entries in a WAL
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/accumulo
ACCUMULO-2041 finished state management in Tablet