simplify convert code

[andrewheumann]

• clean up the Convert functions to use more concise + built-in functions
• rename functions to be clearer (happy to revert this part if you have a strong preference)

[blueherongis]

In the SetCRS branch, I was tinkering around the same area of Convert and doing similar cleanup/renaming. I like yours better, but can we keep “XYZ” instead of changing to “World” in the naming (ie WGStoXYZ)? It’s slightly less ambiguous to me, especially if we add other coordinate systems.

[andrewheumann]

Done