TimedMediaHandler - missing groups

Yes, without documentation translation could be hard. Everyone can do that, if he/she is familiar with the extension.

The missing messages are:

Maybe some more information could be added to:

But this documentation is usually added to git and than reimportet to translatewiki.net, so this needs repository access on gerrit.

Now added with gerrit:338520, waiting now for configuration change of translatewiki.net - gerrit:334504