Create a bootstrap customization app

See the Readme.md file for installation and usage instructions.
Use new bootstrap files
Remove old bootstrap files
Use bs3 classes for navbar
Upgrade base.html indent size to match other files
Disable the useless bootstrap theme css
.container is no longer necessary
Upgrade the almost top navbar to new bs3 classes
Use new classes for icons
Install the django-widget-tweaks app
Simplify the form filtering template
Revert ".container is no longer necessary"

This reverts commit 273ad6894f1424ce83a8940b61d00722c9ebdd61.

Ok, container is still usefull to keep the total screen width <= 100%.
Stretch the .container size to 100%
Enable responsive-table class for larger screens
Hide select / deselect option for small screens
Enable responsive display for document list table
Make it easier to flow content under seconds navbar
Disable the mixin for responsive tables.

Since we don't display filters' column on medium and small screens
anymore, we no longer need to extend the .responsive-table class to
medium screens.
Hide filters's colmuns and small and medium screens

Use the bootstrap off-canvas's example.

See http://getbootstrap.com/examples/offcanvas/
Customize bootstrap to backport some css classes