don't set expos window vals to crop vals if R none
test camera daemon restarting
move scan action() from ueye_camera into camera_base

It would be valid for either our X-theta-z scancam or some future xyz version.
So move it into the base class so that the xyz version could inherit it as
well.

It leaves only the constructor and move() functions as specific to the
xthetaz_scancam class.
check existence of scancam before finally stopping