Fixed countdown and projector update issues

* 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
Merge pull request #1115 from ostcar/projector

Fixed countdown and projector update issues
Show friendly error message when portable dir is not writable (closes #1110)
Merge pull request #1122 from andkit/fix-1110

Fix for issue #1110
Final update of all languages for 1.5: CS, DE, FR, PT.
Merge pull request #1124 from emanuelschuetze/translations

Final update of all languages for 1.5: CS, DE, FR, PT.
translate lanuage names in global_settings

Fixes: #1118
Merge pull request #1119 from ostcar/translate_languages

translate lanuage names in global_settings
Prepare handbook for 1.5.
Update documentation
Add function get_active_object and bugfixes

* Dont throw errors in overlay.get_projector_html if debug == False
* fixe check of active slide in agenda
* Fix #1121
Merge pull request #1123 from ostcar/overlay_error

dont throw errors in overlay.get_projector_html
Updated documentation for 1.5

- Updated all screenshots.
- Improved image handling with autoimage extension.
- Some minor content updates for 1.5 version.
- Fixed wrong list of speakers icon.
Updated metadata files for final release.
Merge pull request #1126 from normanjaeckel/PrepareRelease

Updated metadata files for final release.
Updated README: Removed qrcode. Moved bootstrap.
Merge pull request #1127 from emanuelschuetze/readme

Updated README: Removed qrcode. Moved bootstrap.
Merge pull request #1125 from emanuelschuetze/documentation1.5

Documentation1.5
Added used sphinx extention 'autoimage' to README.

Thanks to author Pedro Kroger who has allowed us to use it under MIT.
Merge pull request #1128 from emanuelschuetze/readme

Added sphinx extention 'autoimage' to README.