Bugfix and Improvement to Registration Editor

- Fixed EditRegistration servlet to accept keys longer than maximum
integer (parseInt doesn't work on entity keys that are higher than
2147483647...)
- All info now folds away if registration is to be deleted
Improvements to E-Mail System

E-Mails are now created with VelocityEngine and templates are stored in
html/email, e-mail contents is also improved with better HTML formatting
(more verbose however much more readable)