Fixed projector template: Removed double <hr> in welcome and custom slide.
Fixed dummy-notification message class and generic new_message function.
Merge pull request #1136 from emanuelschuetze/template-fixes

Template fixes
Fixed http status code when requesting a non-existing static page using Tordado web server. Fixed #1161.
Fixed error when a file was removed from filesystem. Fixed #1120.
Added permission to see participants also to the manager group. See #1150.
Merge pull request #1164 from normanjaeckel/Issues-1.5.1

Fix issues for 1.5.1
Fix list_of_speaker overlay

* Issue a warning message, if a overlay raises a exception
* Fixed #1131
Merge pull request #1165 from ostcar/list_of_speaker_overlay

Fix list_of_speaker overlay
Merge branch 'stable/1.5.x'

Conflicts:
	openslides/projector/projector.py
	openslides/templates/base.html