os_slideshow markup structure matches HC's.  #1557

Markup is the same.  Changed the captions from spans to h2 and p.  Changed the controls to li (and didn't even have to update javascript).

2 differences that I'm aware of.

1. Controls are just an li.  There's no a tag in the li.  That can change if needed but this seems cleaner (although the a tag does have some semantic value here).
2. I don't have a section tag around the whole thing.  That's easily fixed.
Merge branch 'SCHOLAR-3.x' of github.com:openscholar/openscholar into SCHOLAR-3.x