A resubmission of commit 11eaa3d7 in PR #2403 and PR #2443 and continues
the work in #2555 implementing Python bindings to the flow simulator.
The step_init() method initializes the simulation. It is required for the
Python script to run step_init() before calling the step() method (which
will be implemented in a later commit).
A simplified version of PR #2518 that uses a deck filename to construct
the simulator.
After private discussion with @joakim-hove it was decided that the
construction of the blackoil simulator from Python using deck,
ecliseState, schedule and summaryConfig as constructor arguments from
\#2518 should be replaced by a constructor taking only the deck filename
as parameter.
A rewrite of the Python bindings for the blackoil simulator using
pybind11 as introduced in PR #2127. The new version uses the
refactored flow.cpp introduced in PR #2516 and thus avoids duplication
of the code in simulators.cpp.
This PR will be the starting point for implementing the Python bindings
introduced in PR #2403.
