Reinstate tests PF/PPF with proper Surfex Initial conditions files for "prep" task

[AlexandreMary]

From CY49T1, the (some) forecasts tasks of tests PF/PPF (=Prep+Forecast/PGD+PRREP+Forecast) crash, because of inconsistent Surfex initial conditions files.
This chained tests should be reinstantiated with a proper set of initial files (current ones have been rewritten and updated "a la mano" during upgrades of Surfex), as it is an interesting complementary test to check the consistency between these Surfex-related steps, on the occasion of a change of Surfex version for instance.

This series of tests also needs to be improved, as the orography generated in PGD files (unfiltered spectrally) and in atmospheric files is not consistent. One should implement the "trick" of overwriting the atmospheric orography in the PGD, as is done in the PGD/c923 Olive configuration.
(Cf. #12)