AUv2 support

[wrl]

few pre-requisites for this:

• Params should have a hash (or otherwise opaque) u32 ID instead of just an index. this allows for stable automation even when parameters are rearranged.

• we will need some mechanism for wrapping a compiled plugin into a bundle (.component for AUv2), which may rely on cargo-make or similar tool.

• referencing above, metadata defined in the source code will need to make its way to bundle metadata in the Info.plist file. this will be things like AU type, subtype, manufacturer, etc. do we parse the source, or how does this work?