initStateFromDeck: reverse the priorities of the PRESSURE and EQUIL keywords

i.e., if PRESSURE and EQUIL are both present, we now use the first
instead of the second one for initialization. This is convenient for
the Norne dataset as the init data can be simply included from the
main file. Also, one can argue that if both keywords are present, the
user knows what he does and probably has an external tool to generate
the init data. (Though it can be debated if we should print a scary
warning in that case...)

the code paths for the old EclipseGridParser have not been touched...