add last seen mechanism to queues rather than just CEs

[marianne013]

People have been quietly changing queues while retaining the CEs, so our DIRAC slowly but surely accumulates old queues.

[marianne013]

While the side effects are "mostly harmless" this should also be straight forward to implement, no ?

[alexanderrichards]

I assume so

[marianne013]

Of course this doesn't really makes sense for an HTCondorCE with condor (I assume all HTCondorCEs have condor behind them or am I assuming wrong here ?) as they don't really have queues and we just make up the queues. That would just leave the ARCs.