create branch for conditional mutations

git-svn-id: https://svn.apache.org/repos/asf/accumulo/branches/ACCUMULO-1000@1502723 13f79535-47bb-0310-9956-ffa450edef68
ACCUMULO-1000 initial checkin of conditional mutations that does locking on tablet server.  The implementation is pretty far along, but still a good bit to do.
ACCUMULO-1000 made conditional writer use thread pool and work properly when multiple threads call it
ACCUMULO-1000 added close method to conditional writer
ACCUMULO-1000 Cleaned up conditional writer type parameter warnings
added concurrency test for conditional writer
ACCUMULO-1000 compressed iterator config in conditional writer RPC calls
Merge branch 'master' into ACCUMULO-1000
ACCUMULO-1000 added conditional writer error handling and test for error handling
Merge remote-tracking branch 'origin/master' into ACCUMULO-1000
added ability to invalidate server side conditional update sessions
ACCUMULO-1000 modified conditional map to not process tservers concurrently and reuse sessions
ACCUMULO-1000 added TODO
ACCUMULO-1000 fixed a lot of odds and ends
Merge remote-tracking branch 'origin' into ACCUMULO-1000
Merge remote-tracking branch 'origin' into ACCUMULO-1000
fixed compile bug caused by merge
ACCUMULO-1000 Added timeout & config to conditional writer.  Added unit test
ACCUMULO-1000 more timeout handling