Add a multiplayer cave random map

Currently it's restricted to debug-only since it's somewhat experimental.

data/multiplayer/scenarios/Random_Scenario_Cave.cfg

@@ -0,0 +1,75 @@
+#textdomain wesnoth-multiplayer
+
+#ifdef DEBUG
+
+#define PLAYER_CHAMBER NUMBER X Y
+	[chamber]
+		id=player_{NUMBER}
+		require_player={NUMBER}
+		x={X}
+		y={Y}
+		size=5
+		jagged=2
+		[item_location]
+			id={NUMBER}
+			place_castle=yes
+		[/item_location]
+		[items]
+			[side]
+				side={NUMBER}
+			[/side]
+		[/items]
+		[passage]
+			destination=central_chamber
+			windiness=3
+			laziness=2
+			jagged=3
+			width=2
+		[/passage]
+	[/chamber]
+#enddef
+
+[multiplayer]
+    # This id is currently hardcoded by the random map generator of the editor
+    id=multiplayer_Random_Map_Cave
+    name= _ "Random map (Cave)"
+    description= _ "A random map set in a cave. Note: random maps are often unbalanced, but if you have time, you can regenerate them until you get a good one."
+    scenario_generation=lua
+    [generator]
+        id="cavegen"
+        config_name="Lua Cave Generator"
+        create_scenario=<<
+        	return wesnoth.require("lua/cave_map_generator.lua").generate_scenario(...)
+        >>
+        [scenario]
+            name= _ "Random map (Cave)"
+            id=multiplayer_Random_Map_Cave
+            {DEFAULT_MUSIC_PLAYLIST}
+            {DEFAULT_SCHEDULE}
+        [/scenario]
+        terrain_clear=Rb,Rb,Rb,Rb,Rb,Rb,Rb,Rb^Uf,Rb^Ii,Uue
+        terrain_wall=Xue
+        terrain_castle=Co
+        terrain_keep=Co
+        terrain_village=Rb^Vu,Rb^Vu,Rb^Vu,Rb^Vu,Rb^Vu,Rb^Vud,Rb^Vud,Uue^Vud
+
+        map_width=40
+        map_height=40
+        village_density=25
+        nplayers=4
+
+        [chamber]
+            id=central_chamber
+            x=14..26
+            y=14..26
+            size=20
+            jagged=30
+        [/chamber]
+        {PLAYER_CHAMBER 1 3..10 3..10}
+        {PLAYER_CHAMBER 2 30..37 30..37}
+        {PLAYER_CHAMBER 3 3..10 30..37}
+        {PLAYER_CHAMBER 4 30..37 3..10}
+    [/generator]
+[/multiplayer]
+
+#endif