Dropdown in panel header does not inherit its colors

Fix for issue #10627
Removed the unnecessary override and the !important from .wrap

In the sticky footer example there were some weird stuff..
Same fix for the navbar example of sticky footer
remove comma separating the color and the color-stop in -webkit-linear-gradient in the #gradient .vertical mixin.
Resolves #10923

Rebased from #10930
Fixes issue #11122 -- navbar-fixed-bottom border

Enable border-top in .navbar-fixed-bottom
fix #11144
FIx invalid element selector

`kbd` (keyboard) is right, not `kdb`. :P
Merge pull request #11150 from ZDroid/patch-1

FIx invalid element selector
add explicit copyright header to docs CSS & JS files; fixes #11112
even shorter banner; remove space between slash and period
Merge branch 'fix-11112'
copy change, add to buttons anchor section
Merge branch 'master' into navbar-button-docs
Merge pull request #11096 from twbs/navbar-button-docs

Resolves #10923
Warn about IE8 + Respond.js + file:// problem in examples; fix #11019
JS docs: add cross-reference to Getting Started mobile modal section
Merge pull request #11156 from twbs/mobile-modals-xref

JS docs: add cross-reference to Getting Started mobile modal section
Merge pull request #11155 from twbs/ie8-file-proto-respond.js-examples-warnings

Warn about IE8 + Respond.js + file:// problem in examples
(Not HTML) tag way is much better