Apply @color argument to striped gradient

The @color argument is currently not being used for the striped gradient.
Remove progress bar striped @color parameters; use default transparent white.

* If the @color parameter is not removed, the stripes are the same color as the element background color. In this case, the stripes do not appear.
code.less: also set default monospace font for `<kbd>` and `<samp>`
Fixing carousel control positioning

The left control should be positioned from the left, while the right
control should be positioning from the right. Positioning both from the
left results in the right carousel control being incorrectly positioned
(most noticeable with a larger than normal font size).
Add missing methods (rotateX/Y, perspective(-origin) and transform-origin)

Added missing mixins:
rotateX
rotateY
perspective
perspective-origin
transform-origin
Fix #10324: Add opt-in note to tooltip docs

* Re-added a note (now callout) about need to opt in to tooltip docs
* Converted same note in popover section to callout
Docs - Getting started: refactor 'Customizing Bootstrap'
Better wording, avoiding 'invoke', and misc edits
Standardizing on LESS (uppercase) and avoiding the word 'less' where that's easy and sensible.
Removed the '.' from '.LESS' in two instances.
Fixed two more instances of [.]LESS in the text
Don't double border a bordered table within a panel
 account for last child bottom border; use 0 instead of none
fixes #10491: new docs background base64 image
Merge branch 'GSEdits7' of https://github.com/StevenBlack/bootstrap into StevenBlack-GSEdits7

Conflicts:
	getting-started.html
Merge pull request #10025 from barryvdh/patch-2

Add missing methods (rotateX/Y, perspective(-origin) and transform-origin)
fix broke width of containers in docs given change to use width over max-width
Merge branch 'master' of github.com:twbs/bootstrap
Merge branch 'master' of https://github.com/nuttertag/bootstrap into nuttertag-master

Conflicts:
	dist/css/bootstrap.min.css
Merge pull request #9968 from thelukemcdonald/master

Apply gradient stripe @color parameter