Kernel extensions

TODO: possible additional arguments to graphics.defineEffect and their motivation, constraints, etc.

TODO: some ways to interact with already-loaded shaders, e.g. replace the source (non-binary ones), dummy out the source ("removing" shader), updating uniforms array if available, and what all of the above needs to observe. The source-affecting options are mainly throwing a bone to shader editors, so maybe they be an opt-in as well... would it make sense to invalidate other options such as category, time dependence, etc. or are those already in use?

Priority-wise, this is mixed, but I think at the moment everything is related to another idea anyhow.