Fix mixed content warnings for some sites

Removed url protocol for sites that support both http and https:
* vimeo
* youtube
* viddler
* slideshare
* bliptv
* clipfish
* dailymotion
* scivee
* veoh

Removed the following sites which are no longer online:
* 12seconds
* blogtv
* current
* googlevideo
* justintv
* revver
* sevenload
* stickam