ACCUMULO-3147 Refactor ReplicationTable constants
ACCUMULO-3147 Create replication table at initialize, upgrade

  Migrate to all replication code to a built-in system-managed replication
  table instead of the user-space one. Ensure all replication-related tests
  pass. Also fix a small bug in Mock which threw an exception when using
  deleteRows with null start and end rows.
ACCUMULO-3312 Fix incorrect path generation during clone table.

Expanded some ITs to actually cover this in the future.
Merge branch '1.6'
Merge remote-tracking branch 'origin/master' into ACCUMULO-3147
ACCUMULO-3147 Fix replication test bug

  Test was trying to talk to ZooKeeper for MockInstance
ACCUMULO-3314 Add a fair volume chooser to stabilize RewriteTabletDirectoriesIT

The RandomVolumeChooser creates failure potential for the test
due to its random nature. A volume chooser that is stable should
result in a stable test.
ACCUMULO-3315 Wait for the pool to terminate before continuing
Merge branch '1.6'

Conflicts:
	server/base/src/main/java/org/apache/accumulo/server/util/RandomizeVolumes.java
ACCUMULO-3147 Fix ReplicationServlet

  Properly show an informative banner message when the replication table is
  offline.
Merge remote-tracking branch 'origin/master' into ACCUMULO-3147
ACCUMULO-3231 Initial stub out of some scripts to automate use of the merkle tree + some random ingest
ACCUMULO-3231 Add a readme
Merge branch 'ACCUMULO-3147'