added composite index for seq_member_id and gene_member_id to speed up joins from seq to gene (useful for retrieving large bacterial families)
The patch does not account for NULL chr_names
Transcripts on patches may have negative coordinates
Merge commit 'refs/pull/ensembl-github/13'

* commit 'refs/pull/ensembl-github/13':
  added composite index for seq_member_id and gene_member_id to speed up joins from seq to gene (useful for retrieving large bacterial families)
Index to speed-up EG-Bacteria queries