ACCUMULO-1614 use zipfian dist in conditional RW so there are collisions as data size increases
ACCUMULO-1891 sets errorcode to default if it is null during message lookup.

Signed-off-by: Christopher Tubbs <ctubbsii@apache.org>
Merge branch '1.4.5-SNAPSHOT' into 1.5.1-SNAPSHOT

Conflicts:
	core/src/main/java/org/apache/accumulo/core/client/AccumuloSecurityException.java
Merge branch '1.5.1-SNAPSHOT' into 1.6.0-SNAPSHOT
Merge branch '1.6.0-SNAPSHOT'