Update tooltips to not use RGBa colors so IE8 can have tooltips, too
(means we're now using `opacity`).

Fixes #9128

* Builds on the new button styles by requiring a `.btn-default` for the
regular, gray labels
* Updates components examples to show new stuff

Added padding variable for alerts and changed customize.html Warning state (which doesn't exist anymore)

- Fixes #9113 (caret colors in dropdown buttons)
- Darken borders around buttons for contrast in button groups

Also relevant: http://www.youtube.com/watch?v=Ldyx3KHOFXw

- Add new mixin to generate and customize focus state as needed
- Adds variable to set default color
- Include clear disclaimer about customizing this—it's about users', so
don't go making everything bright red and expect them not to be
confused or alarmed.

Relevant issues: #2742, #4185, #7942, #8171, #8610, #9044

In class names:
* large => lg
* small => sm
* mini => xs ("Extra small")

In screen size categories:
* Tiny => Extra small

* Smaller padding on buttons and large buttons
* Same with inputs and large inputs
* Remove about 10px from height of large inputs/buttons and 4px from
regular ones

Fixes #8707 and #8700.

(Also relevant: #8711)

Moved alerts, badges, button groups, buttons, carousel, close to
variables.less and customize.html

* Drop progress bar text-shadow
* Reorganize popover and tooltip vars and fix complier error due to
missing `;`
* Run `grunt`

Moved pager, pagination, popovers, tooltip, progress bars & type
properties to variables.less

In this commit I moved modals.less inline properties to variables.less
and also added those variables to customize.html.

* Reorganize layout
* Add input group var
* Add legend border var

* Update `.nav-divider` mixin to simplify to a 1px line (one value
instead of two in parametric mixin)
* Rename and consolidate dropdown caret vars
* Add vars to Customizer

* Drop the `rgba()` border and fallback because fuck that noise
* Add vars to customizer
* Remove rogue `:`

* Remove dupe hover color var (again, it's not necessary to have it's
own var here since we're controlling it via `opacity`)
* Add to customizer

* Remove `@carousel-control-hover-color` since that's just the same as
the default control color and all we change is `opacity` (it's required
for specificity).
* Add vars to customizer
* Update customizer nav to include new section
* Remove the `li` from the var names
* Consolidate and simplify `text-shadow` vars

moved buttons.less, carousel.less & close.less in this commit

* Place component vars alongside the rest of the component vars
* Redo some of the breadcrumbs code to add a var and remove
`text-shadow`