Support for non-beeb resolutions in image conversion

[simondotm]

Hi Simon,
I've been working quite a lot on the HDMI converter recently including adding a profile system and auto switching support for PC style resolutions so another suggestion I have for your image converter is to have a selectable output resolution. The HDMI converter can now display PC CGA and EGA modes (640x200 and 640x350 respectively) and they are essentially the same as bbc mode 0 which is being interpreted as mode 2 so I could run a similar demo on early PCs at 160x200 and 160x350. Both of those resoloutions would be scaled to 4:3 so the image would have to be squashed vertically for CGA and stretched vertically for EGA.

Originally posted by @IanSB in #1 (comment)