Call trigger('click') on slideshow element.

Poltergeist complains that the parent element is covering it
but that isn't a problem for triggering the javascript event.
Merge pull request #608 from sul-dlss/trigger-click

Call trigger('click') on slideshow element.
Abstract navigation configuration into a related model.
Use main navigation configuration to render the exhibit navbar.
Add configured label to breadcrumbs and sidebars.