Using surface volume for injection rather than reservoir volume.
Chase change in class TransportModelCompressiblePolymer and
function computeInjectedProduced().
Also changed interface to computeInjectedProduced() to take state
rather than individual state variables.
Before, it was a single number for the whole domain. It could vary
with time, though.
Simulator behaviour should be identical before and after this commit.
This touches the classes TransportModel*Polymer, Simulator*Polymer,
and the computeInjectedProduced() functions. The PolymerInflow class
and its usage has been replaced with PolymerInflowInterface, and
a subclass PolymerInflowBasic has been created which provides the
old behaviour (using parameters poly_start_days, poly_end_days and
poly_amount).
