[ENHANCEMENT] Autofocus Range Configuration

[pgriffin17]

Is your feature request related to a problem? Please describe.
We sometimes have focuser issues with PWI4 wherein it cannot find focus (such as due to clouds) causing it to run away to the lower end of the focus travel.

Describe the solution you'd like
We should be able to set a min and max autofocus position to the config - if it is outside of that range at the start of an autofocus routine, it will reset to a nominal focus position (which should also be set in the config).