D2k: Add map importer

This is my initial attempt to create a map importer for Dune 2000 .MAP files. (#4281)
Current status:
 - Imports terrain
 - Imports resources (spice)
 - Imports actors (neutral, atreides and harkonnen; I will add the rest soon)

Issues:
 - Missing tiles from arrakis.yaml tileset file  (#5875)
 - Currently cannot add player references for mission maps

This is 90% working with skirmish maps (from what I've seen), excluding 10% for the missing tiles.
While this will import mission maps as well, the player reference issue does cause some problems there. This can be manually fixed in the `map.yaml` for now. I plan on fixing it properly when there is a Dune 2000 mission file reader implemented (#4280).
A couple of things here:

1. I know what this check is doing, but people in the future may not.  You really should have a comment explaining how the raw ids are matched to our template id / index.

2. This is doing a pile of redundant work for each tile.  You can pull everything but the `t.Value.Frames.Contains(tileTerrainInfo)` and `.Select` outside the loop.