refactor(developer): kmc-kmn now builds .js when needed

kmc-kmn calls into kmc-kmw to build .js when it is needed, rather than
kmc-kmw depending on kmc-kmn. This means examining the `&targets` system store
to determine which files need to be generated.

This also implements the `&displayMap` rewrite for both .kvks and
.keyman-touch-layout as part of the KMW compiler.

I suspect that the next step is to place kmc-kmw into a subfolder of
kmc-kmn, given they are part of the same process, and there is no
practical way to separate out the .js generation from the .kmx
generation.