Add checks during Hamamatsu sensor cooler set

[zacsimile]

This address the Hamamatsu SENSOR COOLER error #5, although I've only tested with a BT Fusion. A check with Flash is also in order. It is possible that the act of setting the parameter, rather than the check, is what kills the program, in which case the logic needs a slight tweak. In the event the cooler set doesn't work (e.g. air cooling is on rather than water cooling),

• The software now checks if SENSOR COOLER STATUS matches the SENSOR COOLER set value, in which case there is no error (following the logic in a similar fix at https://github.com/python-microscopy/python-microscopy/blob/master/PYME/Acquire/Hardware/HamamatsuDCAM/HamamatsuORCA.py)
• It also checks if the SENSOR is in the state of READY, BUSY or ALWAYS, in which case there is no error.
• If SENSOR set does not work and the SENSOR COOLER STATUS is in an Error state, then the original error propagates to the user in a dialog. In theory we could make this more descriptive.

I've left the check for what to do in the event we're setting SENSOR COOLER in an extendable case statement, so we could in theory special case setting of other parameters in the future if we run into additional problems.