~alderwick/pico-uxn

Update to latest Uxn.
Build uxn-boot.h in base directory instead of build/.
Add support for repeating tasks in main loop.
Add proper plugin architecture.
Spacing changes.
Build intermediate stuff in build/, move submodules to lib/.
Export config.h to pico-uxn-sharpmemorydisplay.
Export documentation to pico-uxn-sharpmemorydisplay.
Switch to uxn-fast.c
Update to latest Uxn / Pico SDK.
Reorganise into plugin architecture.
Elaborate on framerate.
Add a couple of pictures.
Add building instructions to README.
Add update rule to Makefile.
Get animation example working.
Load boot ROM from external file.
Add config header file.
Remove USB support.
Next