When creating a pre-reserve, new -n option to specify a name for the
reservation, defaults to "default". All other operations require an
-n option to avoid messing with the wrong reservation. You are not allowed
to reuse a reservation name in a project, of course. Priorities are
probably more important now, we might want to change the default from 0 to
some thing higher, and change all the current priorities.

For bookkeeping, the nodes table now has a reservation_name slot that is
set with the reserved_pid. This allows us to revoke the nodes associated
with a specific reservation. Bonus feature is that when setting the
reserved_pid via the web interface, we leave the reservation_name null, so
those won't ever be revoked by the prereserve command line tool.

New feature; when revoking a pre-reserve, we now look to see if nodes being
revoked are free and can be assigned to other pre-reserves. We used to not
do anything, and so had to wait until that no...