Small changes in problem setup of the implicit 2p2c test: A gas phase with nitrogen and water vapor is injected (instead of solely the component nitrogen) which is composed according to the prevailing conditions in the aquifer. This is realized with the solution-dependent Neumann boundary condition. Exchanged reference solutions for cc and box, which showed tiny differences. Improved docu.

Discussed with Philipp and Bernd, reviewed by Markus

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@11993 2fb0f335-1f38-0410-981e-8018bf24f1b0