Make the text color for disabled buttons lighter

Color contrast was failing in pa11y.  This seems a bug rather than an actual problem, because disabled buttons are considered "inactive", and "inactive" elements do not have a contrast requirement.
add a title to next, previous and slideshow buttons

This is to pass WCAG2.0
Increase contrast of .flex-control-paging li a

The text isn't actually visible, so it is not a big deal.  This is mostly to pass validation.
Increase contrast`.close a` link text

This is to pass the automated testing of WCAG2.0.
Fix contrast for @faded-neutral .zenbox, etc

Convert @faded-neutral from RGBA to HEX.  Automated accessibility checkers can't convert RGBA to HEX, so just use the HEX value.
Use local scripts and styles when testing
Make .rssRow.even text color pass WCAG2.0 AA contrast tests
Make text and links pass contrast tests for WCAG2.0 AA
Fix contrast ratio for wdn_tabs

Use hex values because the accessibility checker (pa11y) can't handle rgba
Fix `incorrect headers` error for WCAG2.0 AA

the message applies to all days, not just the `service_crec` header.
Fix data-table `th` contrast issues
Merge remote-tracking branch 'upstream/develop' into issue-731
add a default alt attribute to poster images for WCAG2.0
Fix contrast ratio for the color animation demo
make the effect types select box accessible
Make the slider handle accessible
Add alt text poster image in the fallback link
Prevent timeouts

With all tests passing, this test case fails due to a timeout.  This is because it takes more than 60 seconds to run, and there is no output if the tests do not fail.  The work around is to add output for every test.  Pear runs the test in another process, then gets output via a stream.  If there is no output from the stream in 60 seconds, it times out.
Use kevin's suggested value
Keep and use the `@tab-background-color` var