ACCUMULO-1689 Add in option to run GC to the config. Set the GC delay to 30s to
account for the fact that we're running in MiniAccumuloCluster and not a real
instance.
ACCUMULO-1689 Merge branch '1.4.5-SNAPSHOT' into 1.5.1-SNAPSHOT

Conflicts:
	minicluster/src/main/java/org/apache/accumulo/minicluster/MiniAccumuloCluster.java