Add Unionizer

This pr addes the unionizer implementation which will take a layers-worth of features and union the 'like' features together into single geometries. There are a bunch of parameters to tweak which are explained in the conf parsing bits. I should add this info to the readme (look for a another commit to this pr). I should also note that this is not tested. I just wanted to get this pr out there for review while I write the tests and documentation. So yeah again, look for more commits.
The appropriate thing to do here is to probably either remove the geometry, perhaps by returning nothing, or return it unchanged.

Keep in mind that some algorithms can, depending on implementation, result in the same geometry, so we'd have to sanitize after every other izer