Updating some SQL comments.
Fixing white-space.
Adding script for importing predb daily dumps as a batch. This script is similar to the one on the forums but does not drop and recreate indexes for each file, making it faster.
Adding TODO to predb daily batch import script.
Adding query to add any missing usent groups to the table.
Removing duplication of the query text.
Removing the IF that is no longer needed as we just added the missing groups.
Improving basic script:

* only print SQL when debugging is enabled.
* DROP the id column which is not needed for the temp table.
* add any missing groups to the table.
* remove the IF for group_id as any that were missing are now added.
Updating Changelog.