Carousel: Use the transition duration from CSS

This makes it possible to change the transition duration in CSS
Fixed single btn in btn-group-veritcal not being rounded
Fixes #11669 - Adds smooth modal scrolling on iOS by default
Don't exclude fonts from bower installs

Excluding fonts/ from bower installs causes glyphicons to be
unavailable to projects using development Bootstrap LESS files.
Drop redundant module import
enable CSS source maps in grunt-contrib-less
hide space characters in input-group-btn to fix segmented buttons double border
Improve pager customization
Add new template, Cover
Issue #11852 : create a new variable for the list group active item link text.
Fix wrong variable name
Merge pull request #11879 from ZDroid/wrong-variable

Fix wrong variable name
Fixes #11801: use correct variables for grid containers
Merge branch 'master' of github.com:twbs/bootstrap
comments and spacing
Fixes #11871: commas last
Merge pull request #11861 from freeman/master

Issue #11852 : create a new variable for the list group active item link...
Fixes #11829: Adds .make-xs-column mixins
Merge branch 'master' of github.com:twbs/bootstrap
Change variable