In Sass, variable must be declared before it is used.
This also removes Miscellaneous section, because horizontal line color
and form / list paddings are Typography.

`@gray-light` darkens from #999 to #777, which puts `.text-muted` at the
threshold for the 4.5:1 WCAG minimum contrast[1]. #777:#fff is 4.48:1.

The “Example” headers in docs become #959595, which is contrast ratio
3:1, the minimum for larger text. Since the headers are less important
than the surrounding text, 3:1 is fine and an improvement on the
previous #bbb:#fff (1.92:1).

Fixes issue #13847.

[1] http://www.w3.org/TR/UNDERSTANDING-WCAG20/visual-audio-contrast-contrast.html

By definition, XS screens have no minimum size, only a maximum size.
(Symmetrically, LG screens have no maximum size, hence why there's no @screen-lg-max.)

change `@zindex-popover` and `@zindex-tooltip` values to be greater than
those set for `@zindex-modal` allowing tooltips and popovers to be
displayed in front of modals (and all other content).

* Removes default max-height from .navbar-collapse (so not every navbar
will get a max-height collapse section)
* Scopes regular 340px max-height to fixed top and bottom navbars only
(those are the only ones that really need a max-height to enable
scrolling)
* Adds a landscape media query for phones to cap the max-height at
200px for fixed navbars"

* The problem with #12674 is that it reassigns the same variable, but the color values were purposely different.
* This uses Less's color functions to generate the proper darker colors.
* Why darker colors? Because those CSS carets render lighter than their solid border counterparts. Consider it a design hack.

Thanks to @Quy for pointing these out.

Add new varaible @icon-font-svg-id and set it to be the correct SVG font ID, used new variable in glyphicons.less

also updates variables file organization (courtesy @mdo)

This changes the order of component variations throughout the repo (code and docs) to be more consistent.
The order now used everywhere is the one most frequently found in the repo before:
Default, Primary, Success, Info, Warning, Danger