Backend changes and sql convenience

- Added sql files to create and drop db and to feed example data.
- Added bridge to import (and later export) data from a gtfs.GTFS object
  to the database.
- Updated models and migrations to implement the whole GTFS reference.

bin/tqdm

@@ -0,0 +1,8 @@
+#!/home/johannes/code/transport-accessibility/bin/python
+# -*- coding: utf-8 -*-
+import re
+import sys
+from tqdm.cli import main
+if __name__ == '__main__':
+    sys.argv[0] = re.sub(r'(-script\.pyw|\.exe)?$', '', sys.argv[0])
+    sys.exit(main())