Organizations => Directories

Added people to "organizations", which means the previous name no longer
makes sense, therefore it's not "Directories".

This name change has been consistently propagated as far as I can tell,
even reflected in filenames.

Changed the name of the database field the event module uses to find the
database where delegate information is stored from `database` to `usedb`
to avoid the need to backtick-escape the name in queries.