* Slightly improve the media experience
- Use a grid to display the list of media
- Add icons for non-image media preview
- Paginate the gallery
- Add links to the gallery in the editor and in the profile settings to make it more discoverable when you need it
Fixes#432
* Allow video and audio tags in SafeString
Otherwise we can't display their preview, nor show them in articles
Also show controls by default for these two elements
* Show fallback images for audio and unknown files, to make them more visible
* Add a new constructor to SafeString when the input is trusted and doesn't need to be escaped.
And use it to generate media previews.
* Make it possible to insert video/audio in articles
* Better contrat for input fields
This change set a white background for input field (text, select and textarea)
to have a better contrast with the page background and improve accessibility for
people with vision problem, and just crappy screen.
This change also remove the round corner for the input to have a clear difference
between editing field and buttons.
This max-width of the form element are a bit bigger too.
* Less space between label and input
This change also remote all units for line-height to have more consistent styles and better cascading support. This solve the too small line height for multi line header in article and also add styling for h1 to h6 (previously h3 to h6 was not styled at all)
