Get rid of superfluous liftIO
Include cstdint instead of boost header
Provide multichannel audio buffer abstraction

Makes it possible to use RAI for sample buffers.
Factor out abstract MessageQueue interface
Make message queue configurable in Environment
Remove references to methcla_init.c
Refactor Methcla::Request interface

Renamed Methcla::Engine::Request to Methcla::Request and removed Methcla::Engine::Bundle. Methcla::Request now has openBundle/closeBundle methods to create (nested) bundle structures.
Add C++ wrapper for Methcla_SoundFile