This also improves Palette so it stores the original RGB888 colors.
Lastly, it adds I2CDisplay as a display bus to talk over I2C. Particularly
useful for the SSD1306.
Fixes#1828. Fixes#1956
Different operations to the display tree have different costs. Be
aware of these costs when optimizing your code.
* Changing tiles indices in a TileGrid will update an area
covering them all.
* Changing a palette will refresh every object that references it.
* Moving a TileGrid will update both where it was and where it moved to.
* Adding something to a Group will refresh each individual area it
covers.
* Removing things from a Group will refresh one area that covers all
previous locations. (Not separate areas like add.)
* Setting a new top level Group will refresh the entire display.
Only TileGrid moves are optimized for overlap. All other overlaps
cause sending of duplicate pixels.
This also adds flip_x, flip_y and transpose_xy to TileGrid. They
change the direction of the pixels but not the location.
Fixes#1169. Fixes#1705. Fixes#1923.
It's designed to minimize RAM footprint by using Sprites to
represent objects on the screen. The object model also facilitates
partial screen updating which reduces the bandwidth needed to display.
This is all handled in C. Python simply manipulates the objects with
the ability to synchronize to frame timing.
