Create event signup page

[misspokeycat]

We should have a page to signup for events that are listed on the EXE calendar.

[misspokeycat]

This is not that difficult to implement, but the big issue is user navigation. Unless we create our own calendar where you can click on events and have that link go to a signup page on our site, user navigation to the signup page would be awkward. This is blocked until we do that.