Adding translate to the SeqRecord

Fellow Biopythoneers,

I'd welcome comments on the idea of adding a translate method
to the SeqRecord object,

https://github.com/biopython/biopython/issues/1103

This case up in some training material where for the flow of the
example, we wanted to parse FASTA nucleotides and create a
translated FASTA protein sequence file.

Also comments on the proposed implementation (eg defaults
and argument order) here please:

https://github.com/biopython/biopython/pull/1144

(If this is merged, since we have a reverse_complement, it would
make sense to include the (back)transcribe methods too for
completeness - here all the annotation could be copies, although
I'm not sure what the defaults ought best to be.

Thanks,

Peter