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.
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