Ontology editor

This is a small CATMAID tool to modify the semantic space of a project. One can add and remove classes as well as relations. Starting from a root node (by default 'root') the class-class links for the current project can be edited as well: it is easily possible to add and remove links. Class-Class links, Classes and Relations are each displayed in an own jsTree. So if the root node is missing, it can be added in the class tree and one can then work on the ontology.

For now, copies of two neuron tracing icons are used for classes and relations. If this is confusing, we can replace them.