Another polymer-specific overload of computeFractionalFlow()
has been added in support of this (this overload deals with
compressible properties.
Also added pressure normalization for situations with arbitrary
absolute pressure.
They do this by using the class PolymerInflowFromDeck
instead of PolymerInflowBasic if there is a WPOLYMER
keyword somewhere in the deck epochs. If there is no
WPOLYMER, the parameters 'poly_start_days' etc. will
be used to construct an instance of PolymerInflowBasic
instead.