Merge pull request #9718 from twbs/bs3_row_margins

BS3: Simpler row margins
fixes #9436 more: put padding on containers, not the body because full width elements
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into bs3_row_margins
un-hardcode @grid-gutter-width in @container-* LESS vars
Removed blank .hidden-print

Blank .hidden-print class doesn't have sense.
Merge pull request #9726 from twbs/calculate-it-son

un-hardcode @grid-gutter-width in @container-* LESS vars
Merge pull request #9737 from ZDroid/patch-1

Removed blank .hidden-print
add respond.js to all examples (fixes #9731)
fix #9743: pager hover background should be light gray
fix for #8768
Fixes #9552: Downsize and use whole numbers for panel title to prevent odd 1px bug
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into 3.0.0-wip
fixes #9538: prevent Firefox rendering bug via some border-fu
add comment addressing #9023
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into 3.0.0-wip

Conflicts:
	dist/css/bootstrap.min.css
more accurate grid classes in examples
mo betta heading examples labels
Update helper classes to reflect changes and mention mixins
2px border on thead th elements for just a tad more separation
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into 3.0.0-wip