Fit b spline se3

[myeatman-bdai]

Add functionality to fit a cubic-SE3-B-spline to data.

[myeatman-bdai]

Converted to draft because this uses scipy functionality not available in the version associated with the dependency list for 3.7 python.

[petercorke]

@myeatman-bdai a few more thoughts on this PR:

• be great to have some more user level documentation and runblock examples, and also to integrate it into the ReST documentation, I can't find the current spline classes by search or table of contents. I'm happy to help out here, but probably need a bit more to go on than what's there (actually the unit tests might be a start for me)
• there's a kinematic/dynamic constrained trajectory generator TOPPRA that might be useful to import, wrap or just play nicely with. I've not used it.

[petercorke]

Converted to draft because this uses scipy functionality not available in the version associated with the dependency list for 3.7 python.

Not sure we should be held back by Python 3.7, it's well past EOL.