ASSERTs in PVTPackage

[francoishamon]

Currently, the PVTPackage relies on ASSERTs to throw errors when the input data is not what is expected. There are two issues with the current behavior:

• These ASSERTs are only executed in Debug, but if something unexpected happens in the PVTPackage we should terminate the simulation both in Release and in Debug.
• Some ASSERTs could be removed. For instance, in addition to the ASSERTs removed in PR Removed ASSERT preventing from running tutorials in Debug #34, I would also remove the ASSERT checking that the pressures are in the table range:
  https://github.com/GEOSX/PVTPackage/blob/e875eaae87bad4504db89c28dc00837e7ebda891/PVTPackage/source/MultiphaseSystem/PhaseModel/BlackOil/DeadOil_PhaseModel.cpp#L104
  and just make sure that if a pressure is outside the table, then we use the first/last value in the table to interpolate in the table (as for relative permeabilities for instance). We could have a logLevel that could be used to decide whether a warning is issued when the pressure is outside the table.