[multidomain] move from PDELab 1.1 to 2.0

Allows to use an unpatched (!) PDELab 2.0 for the multidomain
applications. Users have to upgrade to PDELab 2.0 and the 2.0 release
branch of dune-multidomain. 

- Subdomain GridFunctionSpaces are expected to use
  Dune::PDELab::NoConstraints instead of
  ...NonoverlappingConformingDirichletConstraints. Users have to remove
  the corresponding property settings in the subproblem files.

- Subdomain GridOperators are no longer needed. The property name has
  been removed from subdomainproperties.hh. Users have to remove
  the corresponding property settings in the subproblem files.

- Use OrderingTags instead of Mappers.

- The storage of residual, current and old solution in the
  assembler/model uses shared_ptr now. 

- The components of the multidomain vector containers are accessed via
  the base() method. Everything in splitandmerge.hh still relies on
  EntityBlockwiseOrdering. 

Reviewed by gruenich.



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@13287 2fb0f335-1f38-0410-981e-8018bf24f1b0