index for grouper_audit_entry last_updated

In V4:

Add to the postgres, oracle, and mysql new installation ddl

Add an UpgradeTask that will add the index if it doesn't already exist.  (Hopefully there's a clean way to see if indexes exist across the databases.)

Oracle:

check user_indexes and then 'create index audit_entry_last_updated_idx on grouper_audit_entry(last_updated) online;'

Postgres:

create index concurrently if not exists audit_entry_last_updated_idx on grouper_audit_entry(last_updated);

Mysql: