Add Season Supporter Option

Closes #390 and #389. Makes some other changes to the badge descriptions since I was in there already.
What was the rationale for breaking these out into separate templates?  All of the other places where we do that it's because a snippet of HTML is used in multiple places, e.g. some blocks of form elements and code appear on multiple forms and have enough complexity that they live in their own templates.  Is this going to be displayed anywhere else?