Adds parameter control to ScinthDefs

[lnihlen]

Fixes #6.

• [x] Add parameter parsing to the ScinthDef build phase
• [x] Update file format and add parameters to yaml file generation
• [x] Revive ScinthDef unit testing, add parameters to tests
• [x] Add parsing of parameter yaml on scinsynth side
• [x] Build parameter manifest in AbstractScinthDef
• [x] Add push constants to ScinthDef and Scinth
• [x] Add OSC sending on sclang side to change parameter values
• [x] Respond to OSC commands to update push constants
• [ ] Add fallback to buffer objects if push constant buffer size exceeded (deferred)