this is very convenient during development.
we can then remove the FLOW_BLACKOIL_ONLY option,
as it is no longer needed - use the flow_blackoil binary instead.
however we need to keep this support in Main.hpp due to the python
bindings relying on it.
Expect non-reference type shared pointers arguments instead of references
to shared pointer. This will make it clear to the caller that the called
function is making a copy of the pointer for its own use and not trying
to modify the original pointer of the caller.
Adds a new constructor to Main.hpp that takes shared pointers to Deck,
EclipseState, Schedule, and SummaryConfig. This makes it possible to
share these variables with Python without worrying about lifetime issues
of the underlying C++ objects. For example, a Python script can first
create an opm.io.schedule.Schedule object which is modified from Python.
Then, assume the same Python script creates an
opm.simulators.BlackOilSimulator which is initialized with the same
schedule object. Since the underlying C++ object is a shared pointer,
the Schedule object in Python may go out of scope (get deleted by Python)
without having the C++ schedule object being deleted. And the Python
BlackOilSimulator may continue to be used after the Python Schedule object
has been deleted since it still has a valid C++ schedule object.
