New Coordinate Classes

[BatchelorJ]

This PR adds the following features:

• New classes for coordinates in the form of Cartesian, Geographic and Transverse Mercator
• New class methods to allow for easy coordinate conversion between these types
• Ability to change angular notation for Geographic Coordinates

These features will allow for the following future developments:

• Simplified Helmert Transformation of coordinates in Geographic and Transverse Mercator form (enable Conform7 and Conform14 to take and return coord classes without converting first)
• Standardised Coordinate Uncertainty added to coord classes as an optional attribute, simplified interaction with TransformationSD

[BatchelorJ]

If it's possible, I'd be interested to hear any feedback from @nicgowans before merging too.

[BatchelorJ]

Thanks very much @nicgowans for your comments and feedback. I have implemented the changes you suggested and additionally resolved another couple of bugs in the Ellipsoid/Orthometric/N Value relationships and test data, specifically:

• Line 102: changed Orthometric Height comp from ell_ht + nval to ell_ht - nval
• Changed test_coord cartesian example 1 N Value sign to reflect correct mathematical relationship between Ellipsoid/Orthometric/N Value.

Thanks also for the suggestions of where this development could go long-term. Those are all great suggestions that I think warrant further discussion and exploration of the best way to integrate them into the package.

[harry093]

@BatchelorJ sorry mate, got some NGCA issues to sort and then I'll have a look at this