Script Server: Notify in the perspective button if script errors

[DominicOram]

As an IBEX user I would like to be able to quickly see if a running script goes into error. We currently show whether the script is running or paused in the perspective button, we could also show if it is in error.

Acceptance Criteria

• In discussion with scientists we determine what an error is. EMMA/MUONFE/RIKENFE originally suggested this ticket so they'll be a good start
• When there is an error the user is notified through the perspective button
• There are system tests for this