[BioPython] Copy Constructors for Bio.Seq.Seq?

[Bryan Lunt]

Greetings All!
I would like to make the following humble suggestion:
A copy-constructor for Bio.Seq.Seq would be helpful, currently it
seems that calling Bio.Align.Generic.Alignment.add_sequence on a Seq
object breaks because it tries to initialize a new Seq object on
whatever data you provided, and there is no copy-constructor, nor does
Bio.Align.Generic.Alignment.add_sequence handled just adding a Seq
object directly.

Thanks for considering this, I think this addition will help make
client-code cleaner.

-Bryan Lunt