UI Bug: Handling multiple Problem Locations about quick-fix-scout HOT 2 CLOSED

It turns out that my UI implementation does not handle multiple error 
locations, and that is why SpeculationGrabber (though can handle multiple error 
locations), also was asserting this.

I have updated the UI implementation to also handle multiple error locations. 
Error locations were being used to compute whether a fix is global best fix or 
not (i.e., whether it will fix the current error too, or not). Now, I promote 
whatever best fix that resolves at least one of the error locations returned to 
me by the Quick Fix Processes as a global best proposal. 

While doing this implementation, I also realized a bug that causes duplication 
of the proposals in Eclipse itself. I have also implemented the workaround for 
that bug (so that QFS won't show duplicates).

This issue was closed by revision 0adff0cdcfa1.