Icons for MultiBody package and some sub-packages introduced

git-svn-id: https://svn.modelica.org/projects/Modelica/trunk@6720 7ce873d0-865f-4ce7-a662-4bb36ea78beb
Icon.Example slightly changed so that it has a white background (and is not transparent as before)

git-svn-id: https://svn.modelica.org/projects/Modelica/trunk@6721 7ce873d0-865f-4ce7-a662-4bb36ea78beb