System user other than "SYSTEM"

[ioev]

I noticed in https://github.com/rsim/oracle-enhanced/blob/4ac11553d1e31297b1f7ad421883c9e398e5e9ff/lib/active_record/connection_adapters/oracle_enhanced/database_tasks.rb the system user is hardcoded as "SYSTEM". We currently use a different username to create tables, so it would be nice if the username could be customized similar to the password.

[yahonda]

Thanks for the report. Would you consider opening a pull request?

[ioev]

Sure, I can give that a shot.