Altered:
- SGMBeamline::validateAction and validateActionMessage to use
qFuzzyIsNull rather than qFuzzyCompare
- SGMFastScanActionController::startImplementation() ~ Added check to
see if undulator is forced open, in which case we set the fast scan to
failed.

When #577 is merged back into master, add validateActionMessage to
setFailed() as its optional failure message.
Altered:
SGMFastScanActionController::startImplementation() ~ Changed so that if
Undulator is forced open, then returns false.