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.
Release 1.5
Update version to 1.5.1-dev
Merge pull request #1129 from normanjaeckel/Release-1.5

Release 1.5