Added defensive code for null vertices.
Changed edge collapse code so that it rewrites the IDs on collapsed edges
so that they don't collide with one another. This ensures that collapsed
representations retain their connections to all neighbors. Fixes bug SPC-791.
Changed NodeMapQueryLink so that the menu item won't display if you click on
the background.
Fixed overlaps on circle layout by adjusting calculation of circle diameter.
Fixes bug SPC-794.
Fixed SPC-796 by triggering a state refresh for the dialog box and enabled/disabled
state of the TopologyComponent following a history operation.
Merge branch 'space/13.2' of git://github.com/OpenNMS/opennms into space-13.2