SQOOP-1544: Sqoop2: From/To: ConnectorBean should work support different directions

(Abraham Elmahrek via Jarek Jarcec Cecho)
SQOOP-1556: Sqoop2: Add documentation clarifying connectors vs. engines

(Gwen Shapira via Jarek Jarcec Cecho)
Merge remote-tracking branch 'remotes/origin/SQOOP-1367' into SQOOP-1367