Add documentation about choises with dictionnary

choices={0: "Standard", 1: "Standard2", 2: "standard3"})

The first element is the value, the second is the printed value.

` self.add_parameter("test_F1", "Choices with dict.",default=0, type="int", group="choices options",choices={0: "Standard", 1: "Standard2",2: "standard3"})

    self.add_parameter("test_F2", "Choices with list.",default=0, type="int", group="choices options",choices=[0,1,2])

    self.add_input_file("test_F3", "File choices", required=True, group="choices options", choices={"/home/cnoirot/toto":"toto","/home/cnoirot/tata":"tata","/home/cnoirot/titi":"titi"})

    self.add_input_file_list("test_F4", "File list choices", required=True,
                                 group="choices options",
                                 choices={"/home/cnoirot/toto":"toto","/home/cnoirot/tata":"tata","/home/cnoirot/titi":"titi"})

`