Update the access control API to get rid of the AccessControlProvider interface
and move all of its methods into the abstract AccessControlHandler class.  This
makes the access control API more future-proof because the use of an interface
would not allow the introduction of new methods into the API (such as will be
required for issue #1861) without breaking backward compatibility, and
potentially interfering with third-party implementations.

Also, the access control handler config manager implementation has been
dramatically simplified.

OpenDS Issue Number:  1912