multidomainproblem receives the mdGrid now, this allows to use references...

multidomainproblem receives the mdGrid now, this allows to use references instead of shared pointers; a copy of the multidomain gridview is now stored in the multidomainproblem to get rid of the "reference to temporary" warning

cleanup in multidomainnewtoncontroller, which is now derived from the standard newtoncontroller. The MultiDomain TypeTag is now also derived from NewtonMethod.

Reviewed by Markus


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@12140 2fb0f335-1f38-0410-981e-8018bf24f1b0