Added some functionality from StaticGoldenPathAdaptor.  Added methods fetch_Slice_by_contig, fetch_Slice_by_clone, fetch_Slice_by_gene, and three attendant methods get_chr_start_end_of_contig, fetch_Slice_by_chr_start_end and get_Gene_chr_bp.  Checked generally that these are returning what is expected sequence-wise.