Migrate transforms here and make them work for N-d inputs

[taldcroft]

Description

This moves the transforms RA,Dec <=> ECI here and makes all the transforms (RA, Dec <=> ECI and RA, Dec <=> yag, zag) work for N-d inputs, where the added dimensions are always at the front (i.e. you would have a 25x3 or 5x5x3 input of ECI's).

It also moves the norm function from Ska.quatutil to here and makes it work for multidimensional inputs. There is no explicit new unit test but it is well-covered in the other unit tests.

With this and sot/Quaternion#32 then Ska.quatutil is entirely replaced and can be deprecated.

Testing

• Passes unit tests on MacOS
• Functional testing (new unit tests)

Fixes #102
Fixes sot/ska_quatutil#13

[taldcroft]

@jeanconn @javierggt - please have a look at this in the next few days. I'm desperate to actually complete something technical.