use example_migration from own template folder
video CSS no longer needed
add vimeo and youtube video widgets to the integration task
refactor video widget

+ move controls setting into the DOM
+ remove "embed_url" as it is not needed for the generic player
+ remove projekktor DOM id, as it is generated automatically
+ update specs
use local template folder for example_migration.rb
use correct youtube translation
refactor vimeo and youtube widget models