Post-Processing Functionality

I began work today on implementing post-processing modules. The mGen now loads and keeps track of an unlimited number of post-processing modules and also stores and retains the configuration data, just like generative modules.

The only part left to do is handle the actual generation, in which mGen will have to pass the entire compositional data structure to the post-processing modules and update the structure based on the output of the modules.

Unlike the generative modules, which have permission to view the entire data structure, but can only to add note data to their respective channels, post-processing modules will be granted complete read and write access to the entire set of data to maximize the flexibility of these special modules.