Fixed media_gallery display issues.  #1549

Media gallery thumbnails had a slider class.  So did os-toggle.js (which was responsible for toggling things like the biblio abstract).  Their css was not playing nicely together.

I namespaced our slider to os-slider and updated all the modules I could find that used it.

The two problems in the initial ticket were solved when rogue css wasn't affecting the thumbnails.
Merge pull request #2226 from openscholar/1549-media_gallery_display

Fixed media_gallery display issues.  #1549