Improve const-correctness

Applications/ApplicationsLib/ProjectData.cpp

Applications/FileIO/GocadIO/GocadAsciiReader.cpp

ChemistryLib/CreateChemicalSolverInterface.cpp

ChemistryLib/PhreeqcIO.cpp

GeoLib/SimplePolygonTree.cpp

MeshLib/IO/VtkIO/VtuInterface.cpp

MeshLib/Utils/SetMeshSpaceDimension.cpp

ProcessLib/CreateTimeLoop.cpp

ProcessLib/LIE/Common/PostUtils.cpp

ProcessLib/ProcessVariable.cpp

ProcessLib/StokesFlow/StokesFlowFEM.h

ProcessLib/TimeLoop.cpp

ProcessLib/Utils/ProcessUtils.cpp