add mobile poster image feature for video and background_video pages
Update Changelog

Add note about manual registration of audio loop page type.
bump version to 0.5.0
property og:image:url changed to og:image
Added Cache-Control Header
Added Cache-Control Header
Changed author and publisher in Meta Tags to DIE WELT
Removed setting of cache headers
Title is enough for social media title
Added twitter meta tags, creator name is static! (Maria) - Needs to be changed
Chaged twitter meta tags