Driver for Moog Source, including an interactive layout. No sound. (#12917)

* Driver for Moog Source, including an interactive layout. No sound.

* moogsource: Fix invalid mirroring.
It was a last-minute change from mask() to mirror(), and missed updating map(...).

* moog_source.lay: bugfix - attach `interval` input to the button, not the text.

* Added checksum.

Author: m1macrophage