Add support for per-tile minimap color and height/ramp type.
TileSet cleanups.
Use LeftColor in minimap.
Load tmp(ts) ExtraData for cliffs etc.
Convert TS terrain height, ramp, and minimap colors.
Introduce TerrainTemplatePreviewWidget.
WIP: Hook up basic city buildings.

TODO Footprints.
Add demo map used for news screenshots.
Introduce ActorPreviewWidget and associated plumbing.
WIP In-game map editor.