LinTrain Code

Improved the button ordering on the encoder throttle
Make target to program opto detector with PICkit2 / pk2cmd

Minor documentation and error reporting improvements

Implemented control of loco speed from cabs - the original version acted on
write to a member variable but that's hard in pure Python so use a proper
method. Also removed the undesirable dir -> sign -> dir conversions.
Report errors on accessory command requests and only update the layout GUI
with turnout direction if the request succeeded.
Simplistic controls for static accessories such as building lights
Better accessory naming in dummy mode
Use the XtrkCAD "SWITCHMOTOR" objects to pair turnouts to decoders.
Cope with XtrkCAD's use of "TURNOUT" objects for settrack curves
prog.py:
Hide CV29 bits that are unsupported by the specified decoder (where known)
Support for the new LED accessory decoder
Added a couple of Hornby decoders to the list
Some Python3 fixes

Corrected a capacitor value, added some non-value values
Added a template for a laser-cut and folded chassis

Added a new accessory decoder with eight outputs for LED lighting only.
Ported operations mode CV access to the "light" decoder
Typo fix in the decoder notes

Use a SOT-23 voltage regulator instead of TO92

Bug fix - the operations mode CV write functions were both wrong
- address offset missing for multi-function decoders
- address encoding wrong for accessory decoders
Also implemented the new-style protocol for accessory CV writes

Show some progress messages while reading CVs (as it takes a while)
The workaround for the LTA-1 prototype being broken is no longer active by default
LTCD-1 decoders have CV545

Implemented operations mode CV writes for timings and boost level
Disable charge pump while outputs are on
Clean up timeout code and don't "share" variables unnecessarily
Set the default address to 1 as per the standards

DCC stimulus generator for GPSim now restricts DC bias setting to valid range