Additional functionality for vital Similarity python bindings

[tom-osika]

The Python bindings for the vital type Similarity were completely redone in eeda4bc80625e6be99e119856d20b5a7bfffe48d. There are a few missing features that may be convenient for Python users:

1.) A constructor that accepts a Rotation object of a different template type than the Similarity being constructed. For example, passing a Rotation<float> to the Similarity<double> constructor.

2.) __eq__ and __ne__ only accept Similarity objects of the same template type as parameters. It may be convenient to allow for the comparison of Similarity<float> with Similarity<double>