added gene_description_sources sub
added gene_description_sources sub

Ensembl/ensembl,james-monkeyshines/ensembl,james-monkeyshines/ensembl,danstaines/ensembl,james-monkeyshines/ensembl,danstaines/ensembl,at7/ensembl,willmclaren/ensembl,muffato/ensembl,at7/ensembl,at7/ensembl,at7/ensembl,mjg17/ensembl,danstaines/ensembl,james-monkeyshines/ensembl,Ensembl/ensembl,muffato/ensembl,mjg17/ensembl,mjg17/ensembl,muffato/ensembl,Ensembl/ensembl,willmclaren/ensembl,muffato/ensembl,mjg17/ensembl,Ensembl/ensembl