ACCUMULO-2748 added logic to handle null keys for MockTableOperations.deleteRow

Signed-off-by: Josh Elser <elserj@apache.org>
Merge branch '1.5.2-SNAPSHOT' into 1.6.0-SNAPSHOT

Conflicts:
	core/src/main/java/org/apache/accumulo/core/client/mock/MockTableOperations.java
	core/src/test/java/org/apache/accumulo/core/client/mock/MockTableOperationsTest.java
ACCUMULO-2749 make the DefaultKeySizeConstraint a bit more efficient
Merge branch '1.6.0-SNAPSHOT'
Merge branch '1.6.0-SNAPSHOT'

Conflicts:
	core/src/main/java/org/apache/accumulo/core/client/mock/MockTableOperationsImpl.java
Merge branch '1.5.2-SNAPSHOT' of https://git-wip-us.apache.org/repos/asf/accumulo into 1.5.2-SNAPSHOT
Merge branch '1.6.0-SNAPSHOT' of https://git-wip-us.apache.org/repos/asf/accumulo into 1.6.0-SNAPSHOT
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/accumulo
ACCUMULO-2754 Exclude thrift classes from PMD/CPD
ACCUMULO-2755 fix merge

The new shell module
Means this test to move
Knowing your home: zen.
ACCUMULO-2740 Skip findbugs during release:perform

  It would have already run during release:prepare and adds no value to the
  deployment task.
ACCUMULO-2171 Update CHANGES for 1.6.0-RC5

  Drop 1.4.0 and 1.5.0, as per mailing list discussion at
  http://s.apache.org/YdB
Merge branch '1.6.0-SNAPSHOT'
ACCUMULO-2756 Ensure multiTableTest actually runs

  Check output of launched processes and wait for them to finish before shutting
  down the test.
  Ensure readonly execution waits for tables to exist.
ACCUMULO-2171 Update CHANGES to include ACCUMULO-2756
Merge branch '1.6.0-SNAPSHOT'
[maven-release-plugin] prepare release 1.6.0
[maven-release-plugin] prepare for next development iteration
Merge branch '1.4.6-SNAPSHOT' into 1.5.2-SNAPSHOT
Merge branch '1.5.2-SNAPSHOT' into 1.6.0-SNAPSHOT