Use std::optional replacing boost::optional.

Applications/ApplicationsLib/ProjectData.cpp

Applications/ApplicationsLib/ProjectData.h

Applications/FileIO/AsciiRasterInterface.cpp

Applications/FileIO/AsciiRasterInterface.h

Applications/FileIO/GocadIO/GocadSGridReader.cpp

Applications/FileIO/GocadIO/GocadSGridReader.h

BaseLib/Algorithm.h

BaseLib/ConfigTree-impl.h

BaseLib/ConfigTree.cpp

BaseLib/ConfigTree.h

ChemistryLib/Common/CreateReactionRate.cpp

ChemistryLib/Common/CreateReactionRate.h

ChemistryLib/PhreeqcIOData/CreateEquilibriumReactants.cpp

ChemistryLib/PhreeqcIOData/CreateEquilibriumReactants.h

ChemistryLib/PhreeqcIOData/CreateKineticReactant.cpp

ChemistryLib/PhreeqcIOData/CreateKineticReactant.h

ChemistryLib/PhreeqcIOData/CreateSurface.cpp

ChemistryLib/PhreeqcIOData/CreateSurface.h

ChemistryLib/PhreeqcIOData/CreateUserPunch.cpp

ChemistryLib/PhreeqcIOData/CreateUserPunch.h