ACCUMULO-1312 use Credentials object to avoid serializing as long as
possible
ACCUMULO-802 changed TableNamespaceConfiguration to update it's tables confs when it changes
ACCUMULO-802 added TableNamespaceConfWatcher
ACCUMULO-802 finished adding constraints to namespaces, works correctly.
ACCUMULO-802 removed useless line from testing
ACCUMULO-1312 Fix mapred and proxy serialization issues.
Merge remote-tracking branch 'asf/master' into ACCUMULO-802