Update data-orbit-link with data-orbit-slide

When a orbit slide changes, any data-orbit-link elements that are
linked to the newly active data-orbit-slide will be updated
accordingly. This is done by adding a class of 'active' to the link
that corresponds to the active slide.
Not hard-coding active class anymore

Instead of hard-coding the active class name, I'm now calling the
'bullets_active_class' that was declared with this orbit slideshow.
Merge pull request #2964 from damirkotoric/data-orbit-link-improvements

Update data-orbit-link with data-orbit-slide