removed MoreThanOneSmoothFunctionException
refactored NativeFunctionFactory
added NativeModuleFactory
added ExpressionExecutionTest.executes_call_expression_using_native_function()
fixed generice types of constructor parameters in TaskOutput
added ExpressionExecutionTest.execution_fails_when_native_function_throws_runtime_exception()
added BuiltinSmoothModule with all builtin functions