Should provide video files in the webm format.

[petterreinholdtsen]

Similar to #127, we should provide our videos in webm format, to allow more client software to play our videos. We need to decide which resolution and bit rate we want our video on demand webm files to have.

[petterreinholdtsen]

I guess the first step is to add webm as a format in the videoformat table. I suggest these values:

• fsname: 'webm'
• vod_publish: True
• mime_type: video/webm

Any objections or better proposals? If not, I plan to add it to the database in a few days.