Funsubs Needs an Include Mechanism

[JimTheCactus]

Both for direct loading into a class as well as for piecing together multiple class/pony files. To be honest, using a pony.d folder or something similar is probably the best approach as that allows the ponies to be loaded from any number of files freely. As for the direct load classes they'll be a bit harder but not impossible and will help in contexts where it's known that a large number of ponies will only exist within one class.

The best would be if it could be implemented such that those direct load classes could be brought in at runtime, though opening files is a bit slower.

[JimTheCactus]

The runtime load thing will be looked at in the future as part of #49. I'm thinking I may just make the matrix inverter build a directory of cache files and then pull those in. For now the core intent of this issue has been resolved.