Add functions for improved performance for scalar operations

[taldcroft]

Description

This provides convenience functions quat_to_equatorial and quat_mult which work on a single quaternion. The functions are about 100 and 50 times faster (respectively) than the naive Quat-based method.

This is part of the coupled changes to kadi, chandra_aca, ska_sun, Quaternion, and Chandra.Maneuver to make kadi command states faster.

Interface impacts

Adds functions quat_to_equatorial and quat_mult.

Testing

Unit tests

• [x] Mac (with two new unit tests)

Independent check of unit tests by Javier

• [x] OSX

Functional tests

[taldcroft]

We can ignore the flake8 warning, this will be overtaken/fixed by #42.