Adding the possibility to make intervals like [a; b], ]a; b], ]a; b[, [a; b[

Adding the code for f_exp, f_head, binary_op, multi_op, basic_function_term, list_f_exp, nvList_f_exp in parser/grammar

Adding the init of the functions and the getting of their return (only for number type -> cf. requirement :object-fluent)