Add text mode color themes

[chrisparana]

Utilities for the Apple IIgs or on any Apple II equipped with a VidHD card to set the color of the text, background, and border.

[inexorabletash]

Awesome, thanks! I hope to have a working dev computer again later today.

I think these need a few things but I can handle after merging:

• Use the driver_preamble/postamble .includes which will handle auto-chaining to the next .SYSTEM file (or QUIT if none)
• Make everything conditional on system-detecting a IIgs, so there are no side effects on other systems.
• Replace magic numbers with equates/constants
• Maybe don't force text mode. All the other "drivers" just assume they're running after the ProDOS splash is displayed.

[chrisparana]

I originally used the driver_preamble/postamble .includes, but opted not to in the end. This way another theme can be chose after without rebooting or Herculean catalog rearranging efforts. I don't believe there would be any issue on non-GS machines… either nothing will happen or the colors will be applied if a VidHD is installed (VidHD looks for these values at $C022 and lower $C034 on any II). Forced text mode can be removed.