Fixed serializing and use of restart for the multidomain problems.
Restart of the problem can now be achieved by setting
TimeManager.Restart TIME.
However these changes also changed the reference solutions.

reviewed by Bernd


git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@14158 2fb0f335-1f38-0410-981e-8018bf24f1b0