Removing a TODO in Theme.

Theme resources are cached in ResourceLoader, so there's no need to
cache them also in Theme.
Bugfix: Valgrind now works with Asgard again.

A commit I made last week was causing Asgard to set the sleep duration
between frame updates to an absurdly large number.  This effectively
made Asgard unusable with Valgrind.
Disabling Python support for memory leak testing.

Revert this commit to add Python support back.