mark-h.cha & Adminer::shutDown

[Mark S. Miller <vlad!mark>]

In "mark-h.cha", you will find the following enhancement to the febe
protocol (as we've discussed):  

	SPTR(Adminer) KeyMaster::fetchAdminer()

returns an Adminer object given that the keyMaster in question
includes the authority of the System Admin club (otherwise, it returns
NULL (there is also a KeyMaster::getAdminer which does the expected
thing)).  

The Adminer class's protocol is expected to expand to be the various
actions that only an administrator can perform.  At the moment, the
only such defined message is 'void Adminer::shutDown()'.  The
implementation in ActualAdminer::shutDown() just does a
BLAST(NOT_YET_IMPLEMENTED) at the moment.  This is the method for you
to fill in with the actual technique for shutting down a backend.

Other possible future messages to Adminers:

a) Messages dealing with archiving

b) Warning other users of an upcoming shutdown (for which they'd need
a corresponding Sensor)

c) Monitoring and changing resource use (for various resources)

d) Controlling how & from where this server accepts connections.  In
particular, a brand spanking new Xanadu backend server is shipped with
the Admin club protected only with a Boo LockSmith (that is to say,
unprotected).  Therefore, such a backend should only come up in the
equivalent of Unix's "single-user mode" until the administrator
changes the lock on the Admin club, and tells the backend to be in the
equivalent of "multi-user mode".  (Suggestion due to Michael, I
think).


In short, Adminer's are a new hook that I expect we will be hanging
alot on.