Fix inconsistency between demo and displayed code for modal demo

Fixes #13991

Save "Preview theme" state; resolves #13940

Remove "pointer" cursor on disabled list-group-item

[skip sauce] [skip validator]

Fix popover live demos in docs

[skip sauce]

Fixed apostrophe typo on home page

...at least if you're a writing nerd :P "Bootstrap ships with vanilla CSS, but *its* source code..."

Remove apparent dead code from docs JS

Fix link to compiling info.

[skip sauce]

.bs-docs-navbar class doesn't seem to be used anywhere at all

Delete redundant Grunt info in README (Merge before shipping)

Update cover.css

Conflicts:
	dist/css/bootstrap.css.map
	dist/css/bootstrap.min.css
	docs/dist/css/bootstrap.css.map
	docs/dist/css/bootstrap.min.css

Revert a991cd57.

This reverts commit e31c2edf.

This reverts commit 25ca5131.

Refs #13914
Refs https://github.com/GoalSmashers/clean-css/issues/302