Lots of cleanup everywhere.

* cleaned up the coding style everywhere: NO spaces before or after ->, i.e. $foo->bar();, NOT $foo -> bar();
* added FIXMEs here, there, everywhere
* added some MW-specific thingies to the SQL file (TODO: update.php support, so that running update.php auto-creates the tables)
* tried documenting some stuff
* moved Special:Chat main HTML into a template
* used ResourceLoader to load CSS & JS on Special:Chat
* rewrote MediaWikiChat.js to be more object-oriented

ABSOLUTELY UNTESTED, but it should work. I hope. Assuming that I didn't manage to mess up the JS file or something...