Update pycon.registration app
Move registration templates from symposion to pycon

Since all related code is in pycon rather than symposion.
Move registrations tests to subfolder
GET group registration
First pass of group registration POST logic.
Tests for Group Registration post logic
Add group registration permission via migration
WIP
Refine markup & JS; stylize output; add error messages.
Tests for group registration form
Don't send registration emails
Fix CSS typo
Update doc string
Handle case where presentation has no slot.
Display whether account is existing or newly created
Update styles for group registration alert messages
Create Accounts for registered users so that they can log in.
Switch order of views - easier to read pull request diff
Remove unneeded change
Fix group registration tests for Accounts