Make NormalCursorWrapper a context manager
 -- like django.backends.utils.CursorWrapper since Django #17671
Merge pull request #547 from DrMeers/master

Make NormalCursorWrapper a context manager
Add loading animation for panels. Fix #488.
Optimize used PNGs. Remove unused PNG and GIF.
XML validity.
Toolbar insertion test for middleware

Byte counts of "İ" and "İ".lower() are different.  If the page html
contains "İ", process_response() method cannot insert the toolbar
content at the correct index, and breaks the page content.
Adjust toolbar insertion code to avoid .lower().

Fix #531.
multiply time_taken in cache panel by 1000 not only for total_time, but also for call time