Add schemas for some astropy.modeling models

As I am reading through this and trying out pyasdf I tried creating schemas for `astropy.modeling` models commonly used for WCS transformations. So here they are.

I think only models which don't define an analytical inverse need the `inverse` definition in the schema so only the polynomials have it here. If this is acceptable I'll add the rest of the polynomials.
Perhaps. They certainly represent a 3D rotation. The way it's implemented now they are two different models with different implementation because the angles are predefind and have a specific meaning in terms of FITS WCS ( `CRVAL1`, `CRVAL2` and `LONPOLE`). 
The two models are inverses of each other. Once one is initialized its inverse can be initialized as well by reversing the order the angles are used.