Certain display types should have a distinct demo

[avsa242]

Some display types simply aren't suited to the existing generic GFXDemo.spin, because of e.g. their relatively low pixel count, or a technical reason such as the low refresh nature of electrophoretic displays.

More suitable generic demos should be created for these.

• [x] Low-res dot-matrix displays
• [x] Electrophoretic/E-ink/E-paper displays
• [x] Alphanumeric displays (e.g., 2x16, 4x20)