Support generic modules with server-side rendering

[sthibaul]

Is your feature request related to a problem? Please describe.
generic modules bring a lot of synchronization constraints, since they embed the audio rendering.

Describe the solution you'd like
Another kind of module should be introduced that uses the server-side rendering that was recently introduced for other modules. That way we keep the ease-of-configuration with simple configuration files, and get more rendering flexibility.

Additional context
Depending on the synthesizer, the format of the audio could vary, we'll have to read the meta-data to determine the encoding. For synthesizers that would emit raw data, we could use explicit configuration.

To be noted: some synthesizers' licence forbid this, we'll have to take care of it.