Add two synth arg utility fns:

* synth-args - return a list of the synth's args as keywords
* synth-arg-index - find a synth's arg index
Improve docstrings
Format docstrings
Improve docstring
Breaking change! node-get-control now only accepts one arg and returns
a value. Use new node-get-controls for old behaviour.
Improve sample-player docstring

- this behaviour should probably change though.
Teach find-note-name to handle nil arg - let nil flow through
Teach sync-event to take a single map as an argument - similar to event