Allow embedding of audio and video files

[michaelpollak]

Adding the functionality to embed video and audio files in dl. Based on the request to add youtube videos we discussed this enhancement in #152 .

possibility so that normal uploaded video files also show as videos and not as download (maybe implement in picture field with add file extensions) like the video upload icon in a texteditor

Currently the field type picture has been extended to allow uploading of videos and audio files, in the frontend picture is renamed "Pictures and Multimedia", should add German "Bilder und Medien" later on.

[dasistwas]

@michaelpollak I like the accepted file types settings. Looks great!

Rename to: Mediendateien, Media files,

[michaelpollak]

That's it, looks neat and we hide the settings that are not useful for the chosen media type from the user.
Fogot to add the commit: michaelpollak@36a1283

Please close if this is done, to keep the issues somewhat manageable :) Thank you.