[Constraints] Adapt move of constraints headers ins PDELab
[TypeTree] Fix include statements to deal with move of TypeTree library
[TypeTree] Remove Dune::PDELab qualification from TypeTree namespace accesses
[TypeTree] Adapt to new syntax for registering node transformations

The function is now called registerNodeTransformation instead of
lookupNodeTransformation, and the tag is now passed as a pointer, just
like the other arguments.
Merge branch 'feature/adapt-for-external-typetree'

Make MultiDomain work with the current master of PDELab again.

* feature/adapt-for-external-typetree:
  [TypeTree] Adapt to new syntax for registering node transformations
  [TypeTree] Remove Dune::PDELab qualification from TypeTree namespace accesses
  [TypeTree] Fix include statements to deal with move of TypeTree library