Improvements and bug fixes to parse tree editor:
- Got rid of classList dependency, so the editor now works reliable in Chrome, Firefox, and Safari.
- All the template code more neatly contained into a single element, so multiple instances of trees can go on the same page.
- Attributes of a node (namely POS and Morph info) are saved when updated in new window.
- Changing POS updates the color of the node in the parse tree.