made some caches larger, and made caching in fetch_all more intelligent
made some caches larger, and made caching in fetch_all more intelligent

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