GEM/POLRIS/HRPD samplechanger

As a user of the samplechanger I would like to be able to cope with the device being reset whilst my script is running (e.g. if there is a power blip). When the device resets it stays in the correct position but reports a -1 as a position and will not move subsequently before it is reinitialised.

To do this:
* My script needs to re-initialise the device if, when I request a move, the device errors needing to be reinitialised. It doesn't need this immediately on restart, as the position should still be valid
* The user and instrument scientist needs to be alerted when this occurs, support teams should also be alerted.