Added more systematically-named list_dbIDs and list_stable_dbIDs to replace list_geneIds and list_stable_geneIds; the old functions are still there for backwards compatibilty but now print a warning and call the appropriate list_ function. Common functionality for list_ functions is in BaseAdaptor.pm.

Conserver space by keeping at most two databases locally.  Might
still not be good enough to create deltas for mart.

automated delta building.

Deleted unneeded modules.
Added some text.

Don't recognize 'ADD' in apply.pl.

apply.pl:  Program for applying above delta.

... plus README files.

Inserted example use of map at end.

survives filtering.  I don't really want to do this here, but in a
separate script that I can use from my DAS client.  So it's going to
change soon again.  Possibly.