Throw an exception if the real species name for an alias can not be found in get_adaptor().  Suggested by jm18 on dev.
Throw an exception if the real species name for an alias can not be
found in get_adaptor().  Suggested by jm18 on dev.

Also reformat get_alias() and get_DBAdaptor().

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