microbit: Enable loading of .mpy files.

Code size is increased by about 1k bytes.  Heap usage is similar to before
this commit: on a test suite of large example programs, those that could
run before can still run, and those that couldn't run still can't run.  But
all those that couldn't run before can now run if they are precompiled to a
.mpy.

The v1.0.1 release

The v1.0.0 release.

Update DAL for fix to compass heading north/south mirroring.

Allow button pins to be used as digital-in, update DAL.

Fix soft-reset button when on battery and update DAL.

Error messages without trace info are now scrolled on the display and…

… memory management tuning

Feature freeze and getting ready for final 1.0.0

For testing prior to v1.0.0 release.

The version at https://python.microbit.org/v/1