Investigate compressed texture support

It's not clear what support there is in terms of loading compressed textures.

There is some code written to support loading compressed textures in qt3d and qtbase, but both mention an old chipset and may be outdated.

We should check what state the functionality is in and create some tests and examples that use compressed textures to make sure that functionality doesn't bit rot in future.

This will require creating some compressed textures. Tools for creating ETC1 are available at
http://www.malideveloper.com/developer-resources/tools/texture-compression-tool.php (linux/win) and/or
http://devtools.ericsson.com/node/6 (win))