Migrate video loader into its view

Add a model shared by the loader and the video elememt.
Try to talk about medium instead of video but not very good yet.
Included some non commited changes from before.
Player updates the model's current time on timeupdate

Seems to be the way to go, since the video object cannot generate
backbone events.
Cleanup some code.
Extract seeker in its own view

Manage duration change event on the video.
Interdependance between video current time and seeker.
Cleanup some warnings.
Extract progress display to its own view
Extract playing button into its own view

Add playing state to model.
Fix slow video bug

Player view was updating the medium current time while playing it and
modifying the medium time because of the event generated.
Now player listen to a different event, raised by the seeker.
Extract speed slider into its own view

Fix a bug with toggling playing state when loading another video.
Starting from scratch in parallel files

Using different organisation with less coupling, from
http://coenraets.org/blog/2011/12/backbone-js-wine-cellar-tutorial-part-1-getting-started/
Descriptions drop down in new design
Re-use player view in new design
Use a template for the whole descriptions select
Improve descriptions list and add play button

"Select One" option in descriptions list is now in the template not on
the server.
Add play/pause button.
Remove unused part of descriptions list view.
Seeker and progress views

Reused from previous design with some fixes.
Open description view when description is selected from the list

Replace the existing view if exists.
Add speed control.
Display sections in tree

Switch to appending view el to container instead of passing the
container as el in the view. Didn't work when we removed the view.
Fix bug when selecting default media.
Change the way server handles sections (as a map) and returns it.
Handle visual click and right click on tree
Selecting section changes playable interval

Description view now has reference to content and can change start and
end of playable range.
Reset media to interval start when it reaches the end

Otherwise, it was continuing after the end.
Commit do get everything on my laptop

I'm not sure what this commit does. It's probably unfinished but I need
the latest version pushed to github to start working on my laptop again.