Beta53 test release

Beta53 test release
Support full CGA NTSC artifact emulation on Pi zero 2W or Pi 3 so 8088mph will run.
This uses code written by reenigne one of the authors of that demo
Four colour modes are also correctly emulated.
(Currently not working on original Pi zero, Pi1, Pi2 or Pi4 which revert to the old code that only decodes mono to 16 colours)
Requires a 16bpp frame buffer and will revert to old code if any other bpp selected
You can also change the NTSC decoding using the Artifact Type setting in the palette menu
Note when artifacts are enabled you can cycle through the four phase quadrants using short presses of SW3
All PC CGA and Apple II profiles have been setup to use the new code on appropriate hardware

Other changes:
Fix Spectrum profiles (bright colours not being decoded correctly)
Support PETSCII Robots custom mode on 60Hz C128
Add 50Hz Intellivision profile
Add Nuvo profile (Spectrum +3 timing)
Add Harlequin profile (Spectrum 48K timing - Untested and may need tweaking)
Add proposed C64 Lumacode format for c0pperdragon