Merge branch 'develop' into feature/checkpointing

doc/userdoc.org

src/language/modules/MathFunctionRegisterForVh.cpp

src/language/modules/MathModule.cpp

src/language/modules/SchemeModule.cpp

src/language/modules/WriterModule.cpp

src/language/utils/EmbeddedDiscreteFunctionMathFunctions.cpp

src/language/utils/EmbeddedDiscreteFunctionMathFunctions.hpp

src/output/CMakeLists.txt

src/output/GnuplotWriter.cpp

src/output/GnuplotWriter.hpp

src/output/GnuplotWriter1D.cpp

src/output/GnuplotWriter1D.hpp

src/output/GnuplotWriterBase.cpp

src/output/GnuplotWriterBase.hpp

src/output/GnuplotWriterRaw.cpp

src/output/GnuplotWriterRaw.hpp

src/output/IWriter.hpp

src/scheme/AxisBoundaryConditionDescriptor.hpp

src/scheme/BoundaryConditionDescriptorBase.hpp

src/scheme/DirichletBoundaryConditionDescriptor.hpp