PDI-10657 - Upgrading Drools library

Another attempt at fixing http://jira.pentaho.com/browse/PDI-10657.
The previous attempt has been cancelled (https://github.com/pentaho/pentaho-kettle/pull/237).

- Converted Rules step into a plugin to avoid downstream dependency conflicts
- Upgraded Drools revision to 5.5.0.Final
- Updated OraBulkLoaderMeta.java to remove dependency on Drools
- Added two convenience constructors for Rules.Column