Minor Bugfixes

- Fix bug in Data servlet related to cross group transactions
- Fix possible NPE in Registration servlet
- Fix possible undefined Velocity variable in Admin Panel panel by
adding default $5/test price
- Fix malformed HTML on login page
Update Contest Details
Add Password Changing Functionality
Update to Google App Engine SDK 1.8.3

- Updated from Google App Engine SDK 1.8.1 to 1.8.3