changed: build separate simulator binaries for flow

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.

flow/flow_ebos_blackoil.cpp

@@ -20,7 +20,7 @@
 
 #include <opm/material/common/ResetLocale.hpp>
 #include <opm/simulators/flow/SimulatorFullyImplicitBlackoilEbos.hpp>
-#include <opm/simulators/flow/FlowMainEbos.hpp>
+#include <opm/simulators/flow/Main.hpp>
 
 #if HAVE_DUNE_FEM
 #include <dune/fem/misc/mpimanager.hh>
@@ -75,4 +75,11 @@ int flowEbosBlackoilMain(int argc, char** argv, bool outputCout, bool outputFile
     return mainfunc->execute();
 }
 
+int flowEbosBlackoilMainStandalone(int argc, char** argv)
+{
+    using TypeTag = Properties::TTag::EclFlowProblem;
+    auto mainObject = Opm::Main(argc, argv);
+    return mainObject.runStatic<TypeTag>();
+}
+
 }