Lots and lots of stuff here to make it compatible w/ 1.23 and even so the JS is still buggy as hell

* Basic ResourceLoader & RequestContext support
* Sane directory structure instead of having all the files dumped in the ImageTagging directory
* Support for the "new" (1.19+) logging format
* SQL schema rewritten to conform to our standard conventions
* Moved the hooks into their own file
* Added update.php hook handler + RenameUser hook handler
* Documentation, and lots of it
* Bumped version number from 1.2 to 2.0 because this is a major rewrite

The JavaScript, which is essential to the extension, is broken, but
slightly less so on the initial page load in Firefox 32.0.3 than in
Internet Explorer 8. In IE8, and in FF after dismissing the tagging box
and bringing it back up again, it's impossible to click on certain regions
of the image, such as bottom left or bottom right. If a JS guru knows why
and how to fix it, that'd be awesome, because as it stands, ImageTagging
is right now more of a proof of concept than an usable extension.

This is a BREAKING, BACKWARDS-INCOMPATIBLE CHANGE in every possible way,
but given that ImageTagging last worked with MW 1.10 or so, it's probably
not a big deal.

Change-Id: I8ccce15c0421e65762db1fd0b75476a97b5dce63