Fixes:
* Sanitize user-provided content in HTML (Fixes#2193)
* Fix encoding of search query in prev/next pages (Fixes#2229)
* Fix some issues introduced with #2196:
- Fix alignment of all <h3> elements (Move the inline style from the parent to the <h3> element)
- Add missing comma on 'dir' HTML attribute (Typo introduced by PR #2196)
Code cleaning:
* Remove unnecessary 'each_sclice' + 'each' double loop in ECR files
* Clean the player's <source> list generation code (in player.ecr)
This will prevent, on large pages, the LTR and RTL text to be
far away, on each side of the page. This could happen on channel
and playlists descriptions, when the page is displayed on a large
screen.
