ACCUMULO-2984 adding ability to run MAC against a permanent accumulo instance

Addressing NPEs with existingInstance

ACCUMULO-2984 add test for existing mac using existing instance

Fixing my NPE fix and integrating Keith's test

Adding ability to clean out singleton stuff

Now no longer doing weird things with statics

Warning cleanup

Removing added features no longer needed

Cleaning up minor ticket items

Fixing another Configuration plumbing issue and adding some info statements
Merge branch '1.6'

Conflicts:
	minicluster/src/main/java/org/apache/accumulo/minicluster/impl/MiniAccumuloClusterImpl.java
	server/base/src/main/java/org/apache/accumulo/server/conf/ServerConfiguration.java