#171 Allow same user to check out files on different machines

[Marc Palmer]

SJ cannot handle the situation where the same user
account is used to check out files on different machines.

If you swap regularly between say a laptop and a
desktop PC, you can get in a real mess where SJ thinks
you have files checked out on your PC when they are
really checked out on your laptop.

Sure, using different users for the two machines will solve
this, but it's another user account, another password
etc. and loses the real "who did what" trail.

I suggest generating some key value stored on the client
and server when you first connect to an archive. This will
uniquely identify the client (independent of user) and will
be sent to the server in future.

This way checkouts/in can be made from different
machines by the same user and SJ will not get confused
(nor will the user). An ID string relating to the client
would be useful so that SJ can say "Checked out by marc
on DESKTOP". i.e. the client would prompt at key
generation time for a description of the client config, i.e.
"DESKTOP".

The one problem here is if a client install (key) gets
trashed. Anything checked out by that client would have
to be available for an admin to unlock.