Added vrml display for Gaussian mixture
fixed copyright notices and license terms

Removed stray notices left in source files by copy&paste.  Replaced
references to non-existent "TargetJr Consortium" and "VXL Consortium"
with the actual copyright holders, the "VXL Contributors" at large.
Fixed wording of the terms in vxl_copyright.h to match the BSD license
we have always used and advertised to contributors on SourceForge.