Initialization of SWL-family from EclipseState.  (Needs PR opm-parser/#278.)

This allows consistent initialization from decks where scaling keywords are specified in terms of meta-keywords like EQUAL, COPY, etc.  In particular this includes an unmodified Norne deck.
Note the this change temporarily (until EclipseState catches up) poses restrictions to the use of the ENPTVD keyword (not used in the Norne deck).

The proper question is: What did @andlaus mean  when he wrote this piece of code :)
I've only fixed an obvious bug, but -1.0 is probably exact as it signals a default value.