Make normalize_whitespace usable again

The calls to self.normalize_whitespace fail at the moment
with the error:

  TypeError: normalize_whitespace() takes exactly 1 argument (2 given)

We could just add self as the first argument to
self.normalize_whitespace, but since this method isn't
dependent on self, we might as well make it a static
method.

mapit/management/command_utils.py

@@ -12,6 +12,7 @@ def __init__(self, *args, **kwargs):
     def characters(self, content):
         self.content += content
 
+    @staticmethod
     def normalize_whitespace(s):
         return re.sub('(?us)\s+', ' ', s).strip()