Fix implementation.
Merge master.
Modified accordion split sections for better html conformance.

The previous implementation allowed for accordions to be interrupted by
other elements like block grids.  Now the accordions do not contain a
block grid.  The separate accordion sections can be named and don't have
to be contained within the same dl.
Don't consider unnamed accordion attributes as a group.
Fixed js files path
Orbit: Fix for links not working on some devices

When a user wraps an image in a link inside Orbit, the link should be set to display:block. I have limited this styles to only links that are direct children of the <li>. We don't want to set all links inside Orbit to be display:block (such as links inside a caption).
Bugfix for accidentally closing all accordion panels

When multiple accordion panels are expanded/active (possbile when `multi_expand: true`) clicking on one of the the active panels would close **all** other panels instead of ony the current one.
Update _top-bar.scss

Fix to three issues:

Removing the background from .top-bar-section ul (line 286) prevents bleed through of dropdown background colour onto the top level if ul elements have had padding declared elsewhere

Adding padding: 0; to .dropdown (line 385) ensures that dropdown menus align the the top menu item and sit alongside each other whether or not ul elements have had padding declared elsewhere

Changes to line heights (lines 484, 491, and 549)  make top level links the same height as the Top Bar removing the "overhang" at the bottom, while keeping the line height for dropdown links
add $anchor-text-decoration-hover setting
adding more list variables for flexibility
Orbit: bullets: explicit click handler

Add an explicit click handler to bullets. Previously it was handled
implicitly only with `settings.next_on_click`.
Orbit: next_on_click: only for slides

Narrow down the selector for the `next_on_click` handler to only match
the slides, but not the bullets.
Orbit: bullets: call `_prepare_direction` before `_goto`

This is in line with other calls to `_goto`, which call
`_prepare_direction` before `_goto`.
See commit e577378ae6d772988bfef5f245069be664642fc7.

This fixes the animation when going to a previous slide.
Update _top-bar.scss

Previous Pull request introduces a problem with the JavaScript generated Back links - this fixes that issue.
Update _tables.scss

Allow different background colours anf font size and weight in header and footer (default is use the same as defined by the $table-head-* variables, so is backwards compatible.

Also reduces the depth of cascade needed to override text alignment in td and th elements
Add "fixed" class

Added a "fixed" class so developers can style their fixed nav differently when it's position changes to fixed.

Since it gets removed from the dom and re-cloned each time it switches between fixed and static, there's no reason to remove the fixed class.
Clean up fixed class

I was wrong the first time. Apparently we do need to clean up the "fixed" class. That should do it.
Prevent scroll from completing a full cycle

Prevent scroll from completing a full cycle when quickly go to the next stop.
Otherwise, the animation will be queued and causes unexpected result.
Fix multi-expand as per PR #4941
Threshold implemented & fixed top option added

Threshold option was not implemented - update to implement
Option included to specify the css "top" distance for the fixed element