Fixes for current UCAS layout

Scraper wasn't working any more (looks like a different version of the site?). I've made it work with the current site now so I figured I should share my fixes. 

Since I neglected to bother with frequent commits (oops ;)) I have:
* Fixed the actual scraping
* Switched the datastore key to a UniversityRef-CourseCode format, not sure if codes have changed or something but it didn't like 5 of the same course codes at different universities? 
* Removed the need for usernames - UCAS track doesn't use these, just the ID number and password

p.s. thanks for this, now I don't need to keep checking the track page myself!