remove current HTML-based symbol, add any missing aria-* attributes

* bower.json, package.json: Extend jQuery version ranges to include v3
* NuGet: Bump jQuery to v3.0.0.1
* Docs+Examples: Update jQuery to v3.0.0
* Use jQuery v3.0.0 for JS unit tests
* Update jqueryVersionCheck to allow jQuery v3.x.x

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/fyi @mdo

Note: The selector in dashboard.css that used .page-header was superfluous
    because the margin that it zeroed was already zero even without that declaration.

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flip things around again, no more base class, try out some new stuff to keep responsive flex grid working

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Now that we don't support IE 8 it's safe to do that.

The table includes a border between the two making this unnecessary

Fixes potential problems with iOS9's new viewport behavior - see for
instance https://forums.developer.apple.com/thread/13510

Move them to footer, and remove duplicate ones.

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Fix #17166

Closes #17319 by merging it.

.visible-xs(-block) => .hidden-sm-up

Fixes #17263.
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Shouldn't really happen, but China for example has blocked Google so this should help.

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And add explanatory comments to the Carousel & Dashboard examples regarding holder.js

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Fix issue #15601 — Position of X-UA-Compatible, charset and viewport

Add comment to all examples

The non-responsive is correctly saying 2 instead of 3

plus one example that still used the old <div role="navigation"> and a
fix-up of the callout as per
https://github.com/twbs/bootstrap/issues/15109

Closes #14951 by merging it.

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Added handling of aria-expanded=true/false to collapse.js, updated
documentation to include advice on making expand/collapse controls
accessible, updated examples and javascript documentation to use
aria-expanded and aria-controls (when targetting single collapsible
element, using ID rather than class selector)

Closes #14147.
Closes #14153.

This way, it works in all browsers.

The validator doesn't choke anymore on this and even though it's not spec compliant, it's needed for some IE versions. So until we move favicon.ico in root, this should do the job.