changed 'calculate.cluster.size.moments.from.tree' and 'calculate.cluster.size.moments.from.model' to return a list with entries Mi and Mij

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/colgem@46 edb9625f-4e0d-4859-8d74-9fd3b1da38cb