Coordinate Transform Integration

[keithdoggett]

This PR makes the Proj4 and CRSToCRS classes subclasses of CS::CoordinateSystem and CS::CoordinateTransform, respectively.

It implements as many of the OGC methods as possible with the PROJ API.

Some other minor tweaks were made to match differences in validity handling in RGeo v3.

Breaking Changes

• CRSToCRS: transform_coords renamed to transform
• CRSToCRS: transform renamed to transform_geometry
• Proj4: transform_coords renamed to transform
• Proj4: transform renamed to transform_geometry
• Remove srs_data_test

I think these changes are comprehensive enough to allow us to begin working on the core library again and start decoupling the core gem from this. There are a few other things we could do like add a proper transform_list implementation and maybe add a few other methods to get more info out about the projections, but I think this is workable for now.

[keithdoggett]

Based on discussions with @BuonOmo, we decided it would be better to keep the method names how they are and change the base CoordinateTransform class to use transform_coords instead of transform.

[keithdoggett]

Thanks for the review @BuonOmo