VST3 interfaces

TODO: After merging into master, update this link to just point to GitHub

See docs/vst3.md for more information on how the serialization works.

VST3 interfaces are implemented as follows:

Yabridge class	Interfaces	Notes
`YaComponent`	`IComponent`, `IPluginBase`, `IAudioProcessor`
`YaHostApplication`	`iHostAPplication`	Used as a 'context' to allow the plugin to maek callbacks.
`YaPluginFactory`	`IPluginFactory`, `IPluginFactory2`, `IPluginFactory3`

The following interfaces are implemented purely fur serialization purposes:

Yabridge class	Interfaces	Notes
`YaEventList`	`IEventList`	Comes with a lot of serialization wrappers around the related structs.
`YaParameterChanges`	`IParameterChanges`
`YaParamValueQueue`	`IParamValueQueue`
`VectorStream`	`IBStream`	Used for serializing data streams.

And finally YaProcessData uses the above along with YaAudioBusBuffers to wrap around ProcessData.