take liuqe from expression if not explicitely specified, liuqe.m2 is used if...

take liuqe from expression if not explicitely specified, liuqe.m2 is used if in expression to set liuqe 2, enforces liuqe if given in parameters

git-svn-id: https://spcsvn.epfl.ch/repos/TCV/gdat/trunk@8142 d63d8f72-b253-0410-a779-e742ad2e26cf