Moved the snapToBase() utility function to region.*pp

I've also adjusted the TODO file, which really shouldn't be committed.
Still, it's there now, so it stays. I don't think the logger is going to
be possible any time soon, so I'll probably look into the disconnection
handler.

common/map/region_pager_api.cpp

@@ -24,8 +24,6 @@
 #include "region_pager_lua.hpp"
 #include "region.hpp"
 
-#include <string>
-
 //DOCS: These glue functions simply wrap RegionPagerLua's methods
 
 static int setTile(lua_State* L) {