More work with Ohm's Law -- MP coordinates
  - ColorSlab uses oSim ranges to properly display "reversed" x-axis
  - OhmsLaw can display horizontal cuts and MVA labels
  - LineCut had typo checking for MrSim3D class
  - MrSim creates the y-axis from -y/2 to y/2
  - "Ex" always means simulation Ex (not current coordinate system). GDA_Rename translates.