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.
Here's what I am trying to achieve with this

```
#ASDF 0.1.0
%YAML 1.1
%TAG ! tag:stsci.edu:asdf/0.1.0/
--- !core/asdf
transform: !transform/chebyshev1d
    degree: 2
    coeffs: [c0: 1, c1: 2, c2: 5]
...
```
If it's written like this, those will be passed directly to the model `__init__`.
Is there a better way to do it?