Add line&column support to CodeMirror completion event

Together with a pull request on the resources-codemirror module these changes add line&column support to the CodeMirror completion event.

I've added this because I'm working on a Java compiler based autocompletion module (that needs the cursor location) that can be used in combination with the CodeMirror module to create a sort of simple Java IDE functionality that can be integrated into JSF webapps.