removed the time integration enum and added a time stability

This commit removes the time integration enum so to better encapsulate the integrators. It was replaced with a GetName method. Also a pure virtual time stability method was added to each integrator

Other related cleanup. In

solvers/IncNavierStokesSolver/EquationSystems/StandardExtrapolate.cpp and solvers/IncNavierStokesSolver/EquationSystems/VCSMapping.cpp

Error handling was added to SubSteppingTimeIntegration. Similar methods had such error handling so it seemed to be overlooked. But I did see the step defaulted to 1.

There is also a GetSubStepName method in the Extrapolate replacing get enum). Which seems burdensome. Would it not be better to have access to the substep itself ? However, it is protected.