Add D2K random map generator

Adds a random map generator tailored for the Dune 2000 mod,
D2kMapGenerator.

This map generator has some limitations compared to the RA/CnC
map generator (ExperimentalMapGenerator):

- Symmetry is far less accurate for non-trivial rotations.
- No circular map shapes.
- Unplayable regions are not obstructed and no symmetry corrections
  are applied. This is partly due to mod limitations (e.g., no
  decorative actors), but I've also considered it less important.
- Somewhat higher map generation failure rates, due to more extreme
  play-space requirements.

In order to support the map generator, some additional features are
added to common map generation utilties:

- A "FromTemplates" MultiBrush collection shorthand.
- Path partitioning logic in Terraformer, use to split paths into
  multiple TilingPaths with different segment types.

mods/d2k/chrome/dropdowns.yaml

@@ -26,6 +26,36 @@ ScrollPanel@LABEL_DROPDOWN_TEMPLATE:
 					Width: PARENT_WIDTH - 20
 					Height: 25
 
+ScrollPanel@LABEL_DROPDOWN_WITH_TOOLTIP_TEMPLATE:
+	Width: DROPDOWN_WIDTH
+	Children:
+		ScrollItem@HEADER:
+			Background: scrollheader
+			Width: PARENT_WIDTH - 27
+			Height: 13
+			X: 2
+			Y: 0
+			Visible: false
+			Children:
+				Label@LABEL:
+					Font: TinyBold
+					Width: PARENT_WIDTH
+					Height: 13
+					Align: Center
+		ScrollItem@TEMPLATE:
+			Width: PARENT_WIDTH - 27
+			Height: 25
+			X: 2
+			Y: 0
+			TooltipContainer: TOOLTIP_CONTAINER
+			TooltipTemplate: BUTTON_TOOLTIP
+			Visible: false
+			Children:
+				Label@LABEL:
+					X: 10
+					Width: PARENT_WIDTH - 20
+					Height: 25
+
 ScrollPanel@PLAYERACTION_DROPDOWN_TEMPLATE:
 	Width: DROPDOWN_WIDTH
 	Children: