move processing under schema

[hq9000]

the conceptual view on the system will be:

1. we build the "project" - this step should be easy to understand
2. we compile the prodject into schema with a "compiler"
3. and the schema can be rendered into the real sound

thus the "processing" module's logical place is in the "schema" namespace to reflect the layer it, in fact, belongs.

writing an issue to do it later