Update 6b: Visual Improvements and Collection Filters

No new cars this update, so have a lovely picture of Quagsire instead! What we do have are some pretty hefty visual upgrades to the game including improved CSS and background images for the main tabs, as well as the all-important collection filter system. Sometimes it will just not work and I don't know why, but usually a second try fixes it. I had to recover this update from a merge conflict incident, so there may be some issues I missed - please let me know if you find anything.