Enhance collapsing JS in bootstrap

- do not force a specific dom hierarchy
- always add a collapsed class to collapsed triggers (even in accordion
mode)
Correct border radius of progress bars with only one part
Updated CSS with new sass version
Display milestones description and due date on click
Add link to filter issues from the milestone part on the dashboard
Ability to filter assigned by "*" (reverse for "none")
Stop displaying the milestone number
Correct fullscreen view of an issue
Display "hard" filters on one line