Performance, new Features and many UnitTests

- remove text: 'Event begin' in templates, if events has no related time records
- add UnitTests for DayGenerator
- add new ViewHelper to display dates and times in detail view (Properties.html)
- Call hooks only if in BE-mode (ext_localconf.php)
- removed MM-Tabeles to organizers and locations
- category tree in plugin can now be reduced with a setting in extConf
- now you can spit the plugin into: only images, only text and show both
- added new view to list users events
- user can edit his event now
- add validator for youtube links
- deactivated validators if show or list view was called