Change `hidden-sm-up` to `hidden-md-up` as the clearfix divs should be visible on both `xs` and `sm` devices (widths of 6 columns).

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

Replace the leftover instances with .m-x-auto (and .d-block when necessary)
Closes #19665
Refs #19102
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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

the active class should be moved from the list item to the link item

/fyi @mdo

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These can be replaced by their `.text-xs-*` parallels.
This also avoids any complications from interactions between the responsive and non-responsive classes.
(e.g. `<div class="text-left text-md-right">`)

Refs #18300
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Now that we don't support IE 8 it's safe to do that.