make a delta list of given size
if delta.size == 1 -> assume same delta for all elements, and make a list of
size element equals to delta[0]
if delta.size >= size -> copy delta truncated to size
if delta.size < size -> throw exception
a class to compute delta closure of multigraph.
this is used in conjunction with a Chromatizer to implements delta shuffling
in a multigraph only edges are assumed to be colored (not necessarily vertices)
and polychromatic.
note: color 0 is assumed to be unused (epsilon relation)
For later retrieval, the colors of newly colored edges are
shifted by a specified amount.