Dump assets and "initial" data before rendering starts

Now does preprocessing off of main() instead of in the dispatcher
initializer.

overviewer_core/dispatcher.py

@@ -49,14 +49,9 @@ class Dispatcher(object):
         """
         # TODO use status callback
         
-        # preprocessing
-        for tileset in tilesetlist:
-            tileset.do_preprocessing()
-        
         # setup tilesetlist
         self.setup_tilesets(tilesetlist)
         
-        
         # iterate through all possible phases
         num_phases = [tileset.get_num_phases() for tileset in tilesetlist]
         for phase in xrange(max(num_phases)):