block axis2

[SimonDanisch]

Continuation of #148

This PR does the following:

1. Reimplement GeoAxis as its own layoutable Block
2. Add a new transformation framework which can later be built out to use e.g. geodetic lines
3. Add Geodesy.jl for 2.5D (lat, long, alt) to 3D (earth-centered cartesian) transformation!

[asinghvi17]

This is pretty gnarly to work through, because there are multiple bounding boxes one might care about. So, I propose to split the geoaxis into three separate cases:

1. InputSpaceAxis: an axis whose bounding box is defined by input space. This has curved spines - consider it similar to GMT's axes, in that the spines curve along lon/lat lines. No inverse transform needed, but cannot handle coordinate singularities.
2. NonlinearAxis: a square-framed axis which only applies transformation to gridlines and tick positions. Simplest and easiest to interact with. Requires some kind of inverse transform to get limits.
3. OutputSpaceAxis: an axis whose frame is the border of valid space, i.e., the outline of the circle of the globe in an orthographic projection.

[briochemc]

Sorry if this is just bothering noise, but here are my first notes after attempting to run most_projections.jl. Things look good at first glance, with GLMakie giving something like below

But, I noticed that:

• titles do not appear (I saw that title= does not work "yet" somewhere as a comment in the code already)
• Latitude tick labels show the first/last longitudes instead of the latitude

I also noticed differences between backends (but that may be just on my end?), in particular that with CairoMakie,

• GeoAxes for k ≤ 4 don't show at all
• grids disappear for all GeoAxes after the 5th GeoAxis is added

[briochemc]

Side question to help me contribute: What's your setup to check the docs? I tried to serve them locally with LiveServer.jl but cannot get it to work... Maybe it's because I don't have the same environment? Should the docs/Manifest.toml file be version-controlled?

[SimonDanisch]

@briochemc to be honest, I've always just run the examples, which are included into the docs (GeoMakie/examples/*)...
I added titles and improved the ticks a bit and cleaned up some other things...
I didn't realize how bad tagged GeoMakie is, so I'd say we merge this even though its far from perfect...