Begin discrete functions handling in the language

CMakeLists.txt

src/CMakeLists.txt

src/language/modules/SchemeModule.cpp

src/language/modules/SchemeModule.hpp

src/scheme/CMakeLists.txt

src/scheme/DiscreteFunctionInterpoler.cpp

src/scheme/DiscreteFunctionInterpoler.hpp

src/scheme/IDiscreteFunction.hpp

src/scheme/IDiscreteFunctionDescriptor.hpp

tests/CMakeLists.txt