ACCUMULO-3395 Keep a reference to a single Logger instance.
Merge branch '1.6'
ACCUMULO-3134 Enable file selection and output configuration in compact command
ACCUMULO-2815 wip.
Move around some more stuff
Rip out the doAs from the UGIAssumingProcessor and just track the principal.

Try to approach this as the client address is done. Pull the principal
out of the Sasl server and store it so we can use it to make
a proper TCredentials that will hopefully be seamless for
the other server processes to use (with the Authenticator/Authorizor).
Stub out a shell kerberos authentication token.
ACCUMULO-2815 Stub out a SaslConnectionParams for kerberos.