Let CAS Editor implement IResourceChangeListener

Some functionality to automatically update a opened CAS in the CAS editor if the file was changed would be really nice. I don't know for sure, if this functionality is missing or I simply didn't find it in the code and in Eclipse. In any case, I haven't found a IResourceChangeListener implementation and that is how I would have done it.

The general communication shouldn't be a problem to implement, but - in my experience - updating all necessary elements can be tricky. The interface for changing a view can maybe be used and has probably to be extended.