Add ThreeD module reexporting everything 3D specific
Export R3 constructors, more angle functions
export r3Iso
Coordinate lenses for R2, P2, R3, P3, using type classes
3D alignment functions
Basic scaling on all 3D axes
New function pointAt to construct rotations
Add Haddock comments for coordinate lens classes, refer to Lens in the
type signatures.

[ci skip]
3D documentation fixes [ci skip]
Merge pull request #129 from diagrams/3D-util

3D scaling, alignment, coordinate lenses