More configurable auto generation

[TheEpicBlock]

The way the current poly generation works has bugged me for a while. It's currently impossible to reorder the way blocks are assigned. PolyMc will always fill in the missing entries using the BlockGenerator. The easiest way to get around this is to make a custom Polymap but that has a number of flaws in it. Polys registered using the api only get added to the default polymap and PolyMc's (and Polymer's) resource generation (and the PolyDump method) only operate on the default map.

[TheEpicBlock]

A potential thing I'd maybe like to do is have rules. Instead of registering their polys, mods would register a rule that would apply their polys to their blocks. Then the Polymap can choose if it wants to apply that rule. It might be worth incorporating a config system for this in PolyMc.