Fix 'cannot create column with spatialite -> unexpected metadata layout'

Cf. https://stackoverflow.com/a/21421766

ffdnispdb/__init__.py

@@ -38,6 +38,7 @@ def create_app(config={}):
         def connect(sqlite, connection_rec):
             sqlite.enable_load_extension(True)
             sqlite.execute('select load_extension("mod_spatialite")')
+            sqlite.execute('SELECT InitSpatialMetaData()')
             sqlite.enable_load_extension(False)
 
     app.session_interface = sess