Cleaned up whitespace in layout algo classes. Tweaked spring layout
parameters. Overrode a method in the ISOMLayout so that it doesn't
randomize positions of vertices by default.
Enhanced DefaultLayout so that it positions unknown vertices by default at the
location of a neighboring vertex instead of at a random location. Added some
validation so that edges that are not connected to displayed vertices are omitted
from the graph.
Merge branch 'space/13.2' of git://github.com/OpenNMS/opennms into space-13.2