Now computeFluxes() also sets well quantities.

Namely well_state.perfRates() and well_state.perfPress().
In the process, some overloads of fluid methods were added to
take V arrays instead of ADB arrays.

Simultaneously, coarsened tolerances a bit. Still hardcoded, though.
Added simulator class and program using ImpesTPFAAD.

This copies similar code from opm-core and replaces
CompressibleTpfa with ImpesTPFAAD. Produces same results
for initial simple test cases.