Add oracle oci8 driver

[radovskyb]

This pull request implements the driver interface for oci8 using mattn's go-oci8 oracle driver.

[alienspaces]

You'll need to add oracle to the docker-compose.yml for testing perhaps?

https://github.com/wnameless/docker-oracle-xe-11g

[mattes]

Thanks for implementing! Would you be interested in porting this to the latest v3?

[mattes]

Would you mind changing the target branch to v1 ?

[radovskyb]

Hey @mattes, I've changed the base branch to v1.

As for porting to v3, it's very possible and I probably will in the future, but probably won't be able to for now (busy).