Rename dark/lit++Legend to legend++Lit/Dark
Refactor TileKind content
Don't use any dark paths

We don't have colours for them, anyway (ideally we need 2 colours
per feature and separate 2 for its dark variant, and for paths
we only have 2 total, 3 if we use yellow for currently seen dark tile,
just as in case of normal floor).
Make ambient light the default for tiles