Add an ability to specify a custom list of banks during the build process

Instead of using a pre-built cache, the new banks list will be generated on the fly.

@mmontag, I didn't forgot about you, and I hope, you could make your own "banks.ini" somewhere outside, and build the the thing with it.

This option makes MT32 defaults being set:
- 127 initial volume
- octave-wide pitch bend