Add initial support for static groups.  At present, this does not allow for
nested static groups, but it does handle changes to the set of available groups
and to group membership while the server is online.  It also includes a
backend initialization listener API, which makes it possible for components to
perform custom processing when a backend is brought online or offline, and this
is used to identify all groups at the time that the server is started.

OpenDS Issue Number:  422