Provide same tool support for Confluence configuration as for JIRA

JIRA has a nice config.sh script in /bin directory where it is easy to point the installation to an existing database (Postgres in my my case).

Confluence does not seem to have this. After a clean install of Confluence there is only the confluence.cfg.xml file, but that does not yet contain the XML for any database.

With a similar config script it would be easy to fill in the details for my particular case. Alternatively there could be commented out sections in the XML config that would clearly show what needs to be added.

Also on the website the instructions on server migration is not clear with regards to using an existing database with a fresh install. There is only the small note on the following page: https://confluence.atlassian.com/doc/migrating-to-another-database-148867.html