Work in the UK

This is the final implementation installed in the UK.  Microstepping x4
and Allowable error of 1
After UK trip

1.  Added x4 microstepping (in the field)
2.  Reduced allowable error to 1 (in the field)
3.  Added default home position in the event that the sampled home
position is exceptionally low.  (at ETM)
4.  Reverse error calculation to sigma - delta (at ETM)