- refactored bi-directional editor:
 * created UModule class (custom module class)
 * moved the relevant code into the new class
 * modified custom element to make use of the new class instead of containing all
the code
 * pfew, much cleaner !
- fixed a few scoping issues:
 * apparently polymer on-** event handlers have the element
as scope, not the object whose method is called
 * thus, added back compile, traverseAst method to element,
that call the UModule's methods
- lots of refactoring of element's code , for clarity:
 * cleaned up code used to highlight meshes in 3D view from code
 * seperated highlighting of all instances of a class and highlighting instances
 * cleaned up helpers
 * all 3D view highlighting now done via helper method "addSelectionEffect"