Add Season Supporter Option

Closes #390 and #389. Makes some other changes to the badge descriptions since I was in there already.
I don't think we actually WANT to be checking ``PRICE_BUMPS_ENABLED`` here, because the ``Notice`` class also warns you when preregistration closes, so the way we have it here, you just won't get that warning if there are no price bumps.  A better approach would be to always display the notice, but have the ``Notice`` class check and see if price bumps are enabled.