Moving the embed to it's own CSS file, moving the docs to the Components page with an example, fixing a Glyhpicons list problem in the docs

Also reorders the CSS to place Glyhpicons as a dependency before other components for fewer overrides and less specific CSS.

revert an earlier change to move the component-animations.less file because it fubared modal backdrop .fade usage

Fixes #11770: Move component-animations.less to the utility section of import list to match Customizer

* Adds new "theme" example
* Adds new theme.less file to provide all the overrides and additional
styles for the theme
* theme.less compiles, via Grunt, to two new files to `dist/css`,
bootstrap-theme.css and bootstrap-theme.min.css

* Deletes the accordion.less file
* Extends the panel to be collapsible with our JS plugin
* Supports panel color variations

* Moves input groups CSS into separate file
* Moves input groups docs into the Components page
* Add support for radios and checkboxes in input groups to fix #8679

Removes the icon fonts and associated docs and LESS code from the core
repo and into twbs/bootstrap-glyphicons.

Bring back the label, make it scale somewhat with the font-size of the parent using percentages and ems

* Restore forms.less file
* Overhaul .radio.inline .checkbox.inline to be .radio-inline or .checkbox-inline
* Update docs to reflect changes