Module tags/ratings (WIP)

Proof of concept for http://www.magiclantern.fm/forum/index.php?topic=10537

Possible side effect: each loaded module file is read twice. Can be fixed, but may need tighter integration between TCC and module code.

Also minor: module strings for not-loaded modules are not freed. Important? (would save around 50K of RAM when you move away from the modules menu)