Add sum() and product() methods to Iterables and Maps

##Use cases

    list[1,3,5]: sum() # return 9
    list[1,"3",5]: sum() # return "135"
    list[2,3,5]: product() # return 30

    map[[1,3],[2,2],[3,1]]: sum() # return 6
    map[[1,4],[2,3],[3,2],[4,1]]: product() # return 24

    # etc...