[FEATURE] Integrate Flowplayer and videoJS for accessible media rendering

The key requirements of accessible media rendering are having
synchronized closed captions (taken from the media resource or
provided by an external SRT file) and a synchronized additional
audio description layer. videoJS offers these functionality by
using plain HTML5 features and Flowplayer is used as fallback
to deliver the content with a Flash application. Editors can
then chose in the media content element which strategy of
content delivery to use.

These changes are a result of the BLE project and are taken from
git://git.typo3.org/TYPO3v4/Incubator.git project-accessibility

Change-Id: I00990ca18e2d9743a67a2d248ff23a2cf2ee8b12
Resolves: #31770
Releases: 4.7
Reviewed-on: http://review.typo3.org/6639
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader
Reviewed-by: Steffen Ritter
Tested-by: Steffen Ritter