Selection needs to sort by bbox area

[GoogleCodeExporter]

When items are selected, the selection priority should be based on which items 
are the closest to the cursor.  When multiple items are on top of the cursor, 
the item with the smallest area should be selected first.  For instance, 
clicking on a vertex should select the vertex, not the trace it is on top of.

Original issue reported on code.google.com by igor.izy...@gmail.com on 10 Jul 2011 at 4:33