Support attributes for Oracle Connections

[grbritz]

Oracle connectors use the attributes "schema" and "service" and don't use the "dbname" attribute.

There are at least 14 other connectors which also use the "schema" attribute, so adding support for that attribute will also help support a variety of other connectors.

[Luca-Terrazzan]

I can see this issue has been solved almost 2 years ago but not yet merged to master. @t8y8 Do you think it would be possible to merge the development branch into master?