Added an admin dashboard to see site statistics like usage of various auth mechanisms

Added a 'flag' option on the event approval page to dismiss events from that page
Checkins page: better fixes to stop table overflowing on phone when long names are present

Sadly requires a hardcoded pixel max-width for the user's name.
So if they make an iPhone that's twice as wide it might look silly. Or on android, whatevs.
Add session checkins count to user profile past events