Augmenting213 ontology class icons

This should include the ontology-specific class icons as discussed in #213.

They are displayed in the titlebar of an ontology-show based page and used with every
`fancy_link` on an ontology.

![ontology_class_icons_fancy_link](https://f.cloud.github.com/assets/697338/1230918/6f19ccc2-2817-11e3-8be2-e973fddf5485.png)
![ontology_class_icons_title_bar](https://f.cloud.github.com/assets/697338/1230920/73584a02-2817-11e3-86e6-62e3bba942c0.png)