Resolve GPL licensing issue with scripting-renjin

This component is licensed permissively with BSD, but the scripting-renjin component is licensed GPL because it depends on renjin which is so licensed. We need to remove the scripting-renjin component from core ImageJ2. We can ship it on its own update site.

Locate the scripting-renjin component and trace how core ImageJ2 components are packaged and distributed through update sites. Confirm the licensing boundary and packaging process before making changes; done means scripting-renjin is no longer part of core ImageJ2 and can be shipped independently.

Written by the indexing model from the issue text.