Enabling tests for MIDI objects

[dromer]

So we've been adding some MIDI objects, improvements and several generators that support it.
However some issues have been reported that should be caught during CI, which means we need tests!

We need to create some midi files to test for all the functionality (all midi input objects and at least 16 channels!) and generate "golden" files from pd.

To generate the "golden" files we can probably just use aplaymidi on Linux to send to pd test patches that print to console.

What we could do is use https://github.com/craigsapp/midifile to enable the test-binaries to load in a midi file and load the messages to the heavy objects and create the console output that we can then compare to "golden".

Ideally we do something similar for output, but this may be more tricky. For now I think focusing on input is good enough to get started.

[dromer]

This was actually completed some time ago. Literally using midifile to create the midi files and subsequently read them in the tests!