Remove meaningless volts per pixel setting

[raacampbell]

Currently the user must calculate volts per pixel manually using a crappy procedure. It would be preferable if this value was calculated based on user input as to the hardware present.

Instead add scanner settings for:

• Control value range. e.g. 10 means -10V to +10V
• min/max optical scan angle. e.g. 30 means a scan range from-30 optical degrees to +30 optical degrees

For camera add:

• Objective focal length
• Tube lens focal length
• Camera pixel size in microns

From the above we can calculate:

1. The microns per pixel on the camera
2. mm/optical degree from which we can infer volts/pixel