Adds upgrades to the confirmation page

A rough copy of the javascript and CSS from the form page, altered so
that attendees can't try to downgrade their badge level.
Refactor JS into preregbase

Moves the javascript for badge selection into preregbase. Also moves the
international checkbox hiding function into address.html, and adds a
check for a field to get rid of our last JS error.
Fix checks for payment

amount_extra gets set before the attendee has paid, so this includes
changes to make sure the boxes are only disabled for paid attendees.
Move badge selection boxes

Factors out the badge selection boxes into the currently-unused
badge_choice template, as the html is now being used in several places.
Also adds an is_new check to make sure attendees don't try to convert
their badges to groups.
Add group_id check

Stops the "group" choice from showing for new group members. Editing a
group during registration is a little strange now, but fixing that is
really low priority.
Remove duplicate JavaScript

I accidentally left a block of JS in the address.html, even though it's
already in preregbase. Taking that out.
AC-specific changes for dealers

Implements some minor changes for dealer applications, particularly
hiding the field for website URL.
Track page views for attendees and groups

Tracks every time someone loads an attendee or group /form page, and
logs it in the feed of database changes.
Track page views for budget pages

Adds tracking for budget pages, which requires a work-around to fit into
the Tracking database. Also improves page tracking in general to prevent
500 errors.
Improvements to tracking page views

Removes unnecessary tracking and sessionizing code.
Merge pull request #767 from magfest/dealer_changes

AC-specific changes for dealers
Improve checking for existing IDs

Rearranges the track_pageview function so it checks for an existing id
parameter dynamically, instead of trying to sort through the string
manually.
Merge pull request #772 from magfest/track_page_views

Track page views
Merge pull request #766 from magfest/add_upgrades

Add upgrades to confirmation pages
Merge pull request #60 from magfest/ac-staging

Group fixes and Dealer reg rework