As in previous commit, this was done in the past, but I removed it when
improving `Navmesh` to hold each navvertex instead of calculating tem
during access.
Previously, rail vertices were not stored but generated on demand from
data stored in a `Triangulation<...>`. This functionality is removed in
favor of storing every vertex in `Navmesh`'s own graph built from the
`Triangulation<...>`, which is now afterwards discarded.
Tests still fail and rails aren't added yet, but this is close enough to
completion for me to commit so that I can now go to sleep without
worrying.
Disambiguate between node indices and (teir inner) petgraph indices.
Rename "band index" to "band first seg index", as we identify bands by
teir first segs. Rename "trianvertex index" and "navvertex index"
respectively to "trianvertex node index" and "navvertex node index", as
these point to nodes on the geometry graph and only indirectly to
vertices on the vertex graph.
Rename "triangulation vertex" to just "trianvertex".
Rename "navigation vertex" to just "navvertex".
The standalone word "vertex" was overused and in some cases confusing.
Mikolaj Wielgus