Begin fixing badge numbers

Changes the 8.5 badge numbers, and starts making uber check if they're in range when shifting them up or down.

This isn't a very good solution, but we can use this to fix the staff and supporter badges and make them adhere to the new numbers. Basically, you can select "next available badge" on a Supporter or Staff badge, and it will fix all those badges' numbers... except the one you're actually changing.
Gotcha.  If it makes anyone feel any better, I've written a ton of unit tests for this code for M13 Uber, since this is one of the edge-casey-ist sections of code in all of Uber.

For now it sounds like Dom is going to write a one-off script to fix the badge numbers in the database, and after that we'll go into ``CUSTOM_BADGES_REALLY_ORDERED`` mode, which means that no one will be able to change these badge numbers (when that setting is ``True`` then deleting a badge just creates a gap in the numbers).