Some map rotation tweaks.

Adds a config option for the map rotation chance.
Ups default rotation chance from 50% of round length to 75% of round length.
Moves the procs around.
Adds two new admin verbs:
Force map rotation.
Change map.

code/modules/admin/verbs/maprotation.dm

@@ -0,0 +1,34 @@
+/client/proc/forcerandomrotate()
+	set category = "Server"
+	set name = "Trigger Random Map Rotation"
+	ticker.maprotatechecked = 1
+	maprotate()
+
+/client/proc/adminchangemap()
+	set category = "Server"
+	set name = "Change Map"
+	var/list/maprotatechoices = list()
+	for (var/map in config.maplist)
+		var/datum/votablemap/VM = config.maplist[map]
+		var/mapname = VM.friendlyname
+		if (VM == config.defaultmap)
+			mapname += " (Default)"
+
+		if (VM.minusers > 0 || VM.maxusers > 0)
+			mapname += " \["
+			if (VM.minusers > 0)
+				mapname += "[VM.minusers]"
+			else
+				mapname += "0"
+			mapname += "-"
+			if (VM.maxusers > 0)
+				mapname += "[VM.maxusers]"
+			else
+				mapname += "inf"
+			mapname += "\]"
+
+		maprotatechoices[mapname] = VM
+	var/choosenmap = input("Choose a map to rotate to", "Change Map")  as null|anything in maprotatechoices
+	if (!choosenmap)
+		return
+	changemap(maprotatechoices[choosenmap])