Altered:
- Start and cancel in AMXRFDetectorViews are now virtual protected
methods in case subclasses want to do more with acquisition.

Added:
- VESPERSXRFDetectorView to reimplement start and cancel to use actions
so all XRF are saved to the database.
- Made the old VESPERSXRFScanController code use modern AMXRFDetectors.
Still not tested at all yet though.  Part of #860.