Added missing grid make-column mixins and fixed some inconsistencies

make-column() was still been use to generate "medium size" columns (col-sm), while make-small-column was creating the default columns (col).
I also changed @grid-float-breakpoint to @screen-small, as it was used in make-row() and I think it makes more sense here than the other.
Make visibility utility classes responsive when used as LESS mixins
Removed Glyphicons mention from carousel.less
set img-circle class in percents
Use nav for proper HTML5 ARIA role mapping

http://www.w3.org/html/wg/drafts/html/master/sections.html#the-nav-element

http://dev.w3.org/html5/spec/sections.html#the-nav-element

http://blog.paciellogroup.com/2013/02/using-wai-aria-landmarks-2013/#tablex
fixes #9241: enable collapsing for labels, in addition to badges, when empty
Merge branch 'aria-nav' of https://github.com/kevinSuttle/bootstrap into kevinSuttle-aria-nav
fix indentation
Ensure proper use and location of role="banner"

http://blog.paciellogroup.com/2013/02/using-wai-aria-landmarks-2013/#tablex

http://www.w3.org/TR/wai-aria/roles#banner
Merge pull request #9347 from kevinSuttle/header

Ensure proper use and location of role="banner"
fixes #9279
add event prefixes
fix borked js docs layout, likely from @kevinsuttle's latest PR
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into 3.0.0-wip
fix broken components page, also likely from @kevinsuttle's #9332
fix comment in tooltip
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into 3.0.0-wip
fixes #8900: nuke empty space between panel heading and list group
Merge pull request #9229 from ggam/patch-13

Removed Glyphicons mention from carousel.less
refresh scrollspy after page 'loads'