Basic keyboard accessibility CSS tweaks

Mostly doubling-up :hover styles to also cover :focus, as a first step
to making the framework more keyboard-friendly.
Additionally, fixed two small markup issues in the docs/examples to
make the "Learn more" large primary button-styled links
keyboard-focusable (as without href they're treated as non-tabable
anchors).
Removed touchstart from bootstrap-dropdown.js.
Cleaned up dirty CSS

Used recess rather than less
Keyboard accessibility in documentation

Removed unnecessary (?) and harmful (from a keyboard access point of
view) tabindex=-1 in the documentation examples.
Revert "Keyboard accessibility in documentation"

This reverts commit a809daf2841f65ffac5030b2c6ce6aea60dd6233.
Leave tabindex=-1 alone

It seems that, as misguided as I personally think it is, ARIA does
indeed want dropdown menus not to behave as regular keyboard users
expect them, killing TAB/SHIFT+TAB in favor of cursor keys. Fair
enough, the issue I have is then with ARIA, not with bootstrap. I would
sugges thought that if you really do want to follow ARIA consistently,
*any* navigation bar should also become an ARIA menu, further making it
impossible for keyboard users to use TAB/SHIFT+TAB to navigate through
it, and that these changes should be reflected in the bootstrap
examples as well...
Revert "Leave tabindex=-1 alone"

This reverts commit 370fa45fbe4ee879a626a67bb4df0ec9495102be.
Update Recess version
Update docs/templates/pages/getting-started.mustache

Add meta tag for viewport in the <head>; revise the URL for the latest version of jQuery.
Update less/mixins.less

horizontal three color gradient added
.icon-folder-close same width as icon-folder-open

.icon-folder-close same width as icon-folder-open. this prevents
buttons from wobbling if the icon changes from closed folder
to open folder 
Tooltip positionning on special cases
Unit test for replacing tooltip inside window
lint + wrong comparison
Test for replacing tooltip when resized
works with fixed test
Arrow replacement
No semicolumns
Fix form-actions documentation
Merge pull request #6728 from fredsa/2.3.0-wip

Fix `form-actions` documentation