GeoInterface cleanup needed

[rafaqz]

I noticed a bunch of weird stuff in the geo_interface.jl file during other PRs, like:

LibGEOS.jl/src/geo_interface.jl

Line 59 in 1c12df5

GeoInterface.getgeom(t::AbstractPointTrait, geom::PreparedGeometry, i) = 0

LibGEOS.jl/src/geo_interface.jl

Line 49 in 1c12df5

GeoInterface.getgeom(t::AbstractPointTrait, geom::PreparedGeometry) = nothing

LibGEOS.jl/src/geo_interface.jl

Line 62 in 1c12df5

GeoInterface.coordinates(t::AbstractPointTrait, geom::AbstractGeometry) = nothing

It could also do with some organization and comments

[evetion]

Agreed. The zero seems like a wrong copy. The other two might be required for Aqua? Good to test though.

[rafaqz]

I wondered that too, they at least need "ambiguity" comments if so