Update tvcon for SAIL Data Disc display

[larsbrinkhoff]

Update the protocol to accommodate the Data Disc display and SAIL keyboard.

• Different resolution: 512x480 pixels.
• Different keyboard layout.
• Updates are in scanline segments of 6 or 8 pixels.

[larsbrinkhoff]

Question: add switch to tvcon, or make separate ddcon program?

I would argue the differences are quite small, so a separate program shouldn't be needed. However, an alternative name would make sense.

[larsbrinkhoff]

If the protocol is updated, it would be good to also consider the Logo "color TV".