Bug fix to image container class names

Bug fix to use drupal_html_class() on image container class names so CSS in ucsf-images-universal.css effects them properly.
this just changed last week. please verify if this reversal is indeed what you want. please see https://github.com/erykmynn/ucsf_images/commit/03cbdf2326f392d5af5ca74b4ff8adf78f3239a4