blackoil model: make it work with grid managers other than EclGridManager

and for discretizarions other than ECFV...
finger grid manager: call the finalizeInit_() method of the base class

this grid manager was forgotten to be adapted and fixes a crash...
test driver script: fix off-by-one error when calculating the number of timesteps

(the initial solution also counts but was not counted.)
(navier-) stokes model: adapt to refactorings of output writing routines