(fix) URLs containing networks with slashes are now handled properly.

Since there were no URL patterns for networks given as IP addresses with masks (e.g. `10.24.1.0/24`), such requests were resulting in 404 errors - the following pull request fixes this problem.

Unfortunately, Django replaces `%2F` with `/` - hence kind of "elaborate" patterns in `urls.py` (for relevant discussion see: https://code.djangoproject.com/ticket/15718).