Put all tables of a dataset in the same tablespace

...and allow us to control the location of its future copies by setting
the tablespace on the dataset's logtable.
Maintain a separate audit log for datasets

This information is in global_log too, but I think global_log will be
going away.
Use the audit table instead of the log table to guide namespace selection
Sweep away the last vestiges of the global log

It wasn't used for anything, so it was just a bottleneck at the end of
transactions.
Enable c3p0 connection pooling, and set the appname on postgres connections