This generally largely drawings from groupings. We need this because it
will be easier to handle all groupings on the level of layout as
continents and bands, which are groupings too, are to be tracked there.
There's a lot of rough edges when it comes to typing and contracts.
The geometry graph is where the layout's dots, segs, and bends are
stored. The connectivity graph is where information about connected
components and relations between tem (e.g. which ones are connected with
bands) and information common to all band primitives are stored.
This removes dependency on the Slab library. We may go back to it
sometime in the future if we decide to phase out usage of Petgraph's
`StableDiGraph`.
I've temporarily removed collision/infringement detection in
`.move_dot()` because it was a lot of effort to get it right. We'll deal
with this later.
There's a panic due to mesh edges not being generated properly from
loose bends. But this commit is already very large, so I'm going to fix
this in the next one.
There's also some nomenclature changes.
It will be possible for the mesh to contain additional vertices that
aren't part of the Delaunay triangulation. `Mesh` is now a wrapper over
`Triangulation` that implements the same traits, and will be later
adding its own vertices in addition to the ones from triangulation.
Mikolaj Wielgus