addressing #9189 manually, part 1: code and pre vars
addressing #9189 manually, part 2: dropdown header and disabled link colors (and refactor commenting styles)
spacing
addressing #9189 manually, part 3: forms
addressing #9189 manually, part 4: input group background var
addressing #9189 manually, part 5: don't bother with a .label font-weight var and let's just use bold because windows hates 500
addressing #9189 manually, part 6: add a navbar margin var, but avoid the navbar-nav var because that should really be customizable
Refactor navbars to simplify things

* `.navbar-brand` is no longer centered, thus removing need for
max-width and a few lines of code
* Clear floats of `.navbar-brand` in the `.nav-collapse` like we did in
2.x, thus simplifying some clearing and other things.
* Restyle the `.navbar-toggle` button to align it's bars up with the
text and flow of the document.
* Restyle the `.navbar-brand` to not use padding on left/right as to
avoid negative margin and other fuckery. This limits the ability to put
a bg color on the brand, but I think that's fine for now.
Follow up commit: fix collapse clearing and navbar brand/nav spacing
Restore prior docs spacing
Drop the font-weight on panel labels since heading elements already get it
addressing #9189 manually, part 7: thumbnails vars
Customizer field updates for variables
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into 3.0.0-wip

Conflicts:
	dist/css/bootstrap.min.css
add another var
Merge branch '3.0.0-wip' of github.com:twbs/bootstrap into 3.0.0-wip