Altered:
- SGMBeamline ~ Added extra documentation to functions which return
standard Actions (createBeamOnActions3(), createTurnOffBeamActions(),
createStopMotorsActions3(), createVisibleLightOnActions3(),
createGoToTransferPositionActions3(),
createGoToMeasurementPositionActions3())

I have assumed in the documentation (and when writing the
createVisibleLightOnActions3) that addSubAction() adds to the end of the
list, not the front and that sub actions are run from front to back. If
this isn't the case, let me know.