From a conversation in jabber and following on from
It would be good to have an array somewhere containing all information about plugins, where their db directories are etc. At the moment get_db_directories seems to contain most of this information but there are other places in moodle that duplicate this (the example was events_load_def).
If we could maintain one array containing this information and then a few helper functions around it we could potentially:
a) remove a lot of duplication
b) make it easier to add new plugin 'types' later without having to add db location information in muliple places