The persistence plugin should allow creation and configuration of multiple persistence units

The persistence plugin sets up only one persistence unit - "forge-default". Successive executions of the persistence setup command will recreate this persistence unit. Multiple persistence units would have to be manually created by hand.

Considering this, it would be good to have the persistence plugin support the creation of multiple persistence units.

Additionally, the plugin should also allow for (re)configuration of the persistence unit, so that a PU once created should not require manual editing.