remove console.log from debug
Add in right-click handling.  Right clicking in the window will find
the closest MathCommand and call its contextMenu method with the
cursor passed in.  If no MathCommand is found, the root object receives
the contextMenu request.  No handler does anything right now.
Enable right click handler for matrices.  Will give user the ability to
add/remove columns and rows by right clicking within the matrix itself
NOTE: this behavior assumes that JqueryUI menu widget is loaded.