Generalise geomtypes

[rafaqz]

This PR allows creating points with any Real numbers.

It also cleans up the code generation code used for createpoint etc, simplifying and reducing indentation level.

Closes #304

[yeesian]

Thank you for this! It seems the only remaining method to be covered is createmultipolygon(::Vector{Vector{T} where T}). Apart from that, the rest seem to be pertaining more to some of the GeoInterface methods to be implemented.

[rafaqz]

Sorry where is the missing createmultipolygon? I can't see where that was even originally implemented.

Edit: sorry I see it's just missing types on in the tests.

[yeesian]

The implementation looks much cleaner, and the drop in test coverage is a weakness of the tests rather than the implementation so this LGTM, thank you!

I appreciate some of the additional tests you've added! Additional increases in test coverage can happen in the future is isn't a blocker here from my POV.

[rafaqz]

Yes sometimes when you delete code you delete more lines that were covered than lines that weren't, so it looks like you've reduced test coverage. But the amount of funcitonality covered hasn't actually changed.