ScalarSolver: Do not use protected base class members
Refactor ScalarSolver so it does not directly access protected members from SolverBase anymore. See http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rh-protected
Refactor ScalarSolver so it does not directly access protected members from SolverBase anymore. See http://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#Rh-protected