Changed api for main menu entries.
Enhanced http error pages using a classed based views.
Moved dashboard and select widgets view from projector to core app.
Also some small clean ups.
* agenda_item.get_absolute_url('projector') returns the activate-url of the related slide.
* agenda_item.is_activate() returns True, if the related item is active
* Fixed set_active_slide to accept kwargs
* Reset countdown when saving a new duration time
* Update countdown overlay when begin_speak and end_speak is called
* Fixed blinking countdown
Fixes: #1078, #1076, #1075
* Set a static projector title
* absolute_urls for the activate links
* update the projector when a slide changes (in save())
* insert the absolute_url template filter
* Preview to slides
* renamed is_active to is_active_slide
* The SlideMixin has to come before the PersonMixin
* Update list of speakers
* Render Countdown via JS
* Reconnect projector after connection lost
* Overlays can allways be active and do not appear in the widget
* Rewrote the clock as overlay
- Fixed agenda widget for special slide views (e.g. list of speakers, summary).
- Fixed back to motion(s) link
- Set icon for list of speakers widget.
- Fixed overlay widget layout of form elements.
- Added submenu with other config_pages to version.html.
- Updated completly DE translations, fixed EN strings.
- Coding style: Use correct ugettext and ugettext_lazy strings. Use "as _" for ugettext only.
Updated translation.
- Improved projector template (clock image, fixed facicon, added subtitle for list of speakers)
- Changed permission strings ('oneself'). Added check if group(pk=3) exists.
- Added event name and description to base template. Some minor template layout fixes.
- Use static subtile (no context var). Show last 2 old_speakers for projector.
- Cut old_speakers.
- Projektor template style changes (e.g. overlay list of speakers).
