match ud calculation between dbgb and dbbmm

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/move@472 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
start adding getMotionVariance

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/move@473 edb9625f-4e0d-4859-8d74-9fd3b1da38cb