Adds fully implicite black oil solver working with CpGrid

This pull request uses the corresponding pull request OPM/opm-core#496, and OPM/dune-cornerpoint#72 and adds a variant (examples/sim_fibo_ad_cp.cpp) of afully implicite black oil solver that uses CpGrid instead of UnstructuredGrid.

As a consequence dune-cornerpoint becomes a suggestion for opm-autodiff
The patches are tested with an SP1 example that Atgeirr provided me with. It seems like one gets the same results as with UnstructuredGrid. As we use the VTKWriter of DUNE for output and need the parallel version to pass it a path, the produced file names are different.

Please note that parts of the contents of opm/autodiff/GridHelpers.[hc]pp should probably be move to dune-cornerpoint for broader use.