Merge branch 'feature/det-and-inverse' into 'develop'

doc/userdoc.org

src/language/modules/MathFunctionRegisterForVh.cpp

src/language/modules/MathModule.cpp

...language/utils/EmbeddedIDiscreteFunctionMathFunctions.cpp

...language/utils/EmbeddedIDiscreteFunctionMathFunctions.hpp

src/scheme/DiscreteFunctionP0.hpp

tests/test_BuiltinFunctionProcessor.cpp

tests/test_DiscreteFunctionP0.cpp

tests/test_EmbeddedIDiscreteFunctionMathFunctions.cpp

tests/test_MathModule.cpp