Exclude debug script.
Fix regression in ve.ce.MathNode.

ve.ce.ClickableNode has been removed.
Remove obsolete script include.
Override inherited rendering of highlights in ve.ce.MathNode.
Fix regressions in MathInspector.

There have been introduced several major problems:

- after inserting a node, fragment.getSelectedNode() does not work
  for math block nodes
- fragment.removeContent() does not work as a wrong range is used
- fragment.changeAttributes() does not work anymore, as it skips changes
  to nodes with 0 length

As a solution I switched to more general and lower-level API.
Clone MathNode's default attributes when creating new nodes.

Fixes #2
Minor cleanup in MathInspector.
Deactivate some animation transitions to improve the user experience.
A workaround for a selection glitch after dismissing a MathBlockNode.