TextDisplay feature: allow other fonts (and related features)

[JoeStrout]

TextDisplay currently uses always the "normal" font (one of four built-in fonts supported by PixelDisplay), and always 26 rows by 68 columns.

In Mini Micro 2, let's allow the user to change the font of a TextDisplay to any of the built-in fonts, or even supply their own font. Specifically:

1. Let the user select "small", "medium", "normal", or "large" (matching PixelDisplay.print).
2. Let the user supply a font image, a cell width/height, and either a list of Unicode code points corresponding to the cells in that image, or a string like "32-97,129,135-147,SKIP 7,2837-2894". (The string format allows single numbers, a range of numbers, or a "SKIP" command that skips over that many cells in the font image.)
3. Give TextDisplay width and height (or maybe columns and rows?) properties that report how big the display is; by default, this will be sized automatically to fit the screen.
4. Let the user change that (similar to a TileDisplay), and also scroll by pixels or rolls, enabling text displays larger than the screen.

Everything will be set up so that by default, it looks and works exactly like the current TextDisplay (except on shorter screens, where the default display will have fewer rows; see #47). But the above features will give the power user the ability to set up a TextDisplay to suit their needs, without having to use a TileDisplay and recreate all that functionality themselves.

[JoeStrout]

Incidentally, here are the columns x rows we'd get with each of the standard fonts:

Font	960 x 640 screen	960 x 600 screen
small	120 x 45	120 x 42
medium	87 x 33	87 x 31
normal	68 x 26	68 x 25
large	48 x 20	48 x 18

[dcrawl]

That would be awesome! I had to create a child of PixelDisplay to create my TUI because I wanted to use my own font.

[JoeStrout]

If you want to do stuff like this today, you'd be better off using a TileDisplay rather than a PixelDisplay. Everything outlined above (plus all the standard TextDisplay functionality) could be written in Mini Micro, and run efficiently, using a TileDisplay.

But obviously it'd be better to have this built in!