Move reprs to Python

[henryiii]

Currently, we use reprs in C++. We should move those to Python; this will help them include the correct class name, and might be simpler to maintain in the long run.

We will need to improve the internal inspection capabilities a bit for this; currently you cannot get the power used for the regular with power transform.

@HDembinski originally had this idea.

[HDembinski]

The regular axis has a transform() method, which should be exposed as a read-only property. This can then be used to query the transform used and the power value in this case.

[henryiii]

Closed by #200.