Added unit test about outgoing values selector that cannot be resolved

Hi Chris,

here is one query that seems to cause problem in the cascading planner. It looks like that the cause is related to variables using a different table alias, but the same column name.

```
Caused by: cascading.pipe.OperatorException: [{0}lhs*rhs][cascading.lingual.optiq.CalcProjectUtil.addRename(CalcProjectUtil.java:117)] could not resolve outgoing values selector in: Each({0}lhs*rhs)[Identity[decl:'CITY']]
	at cascading.pipe.Each.resolveOutgoingValuesSelector(Each.java:408)
	at cascading.pipe.Each.outgoingScopeFor(Each.java:384)
	at cascading.flow.planner.ElementGraph.resolveFields(ElementGraph.java:628)
	at cascading.flow.planner.ElementGraph.resolveFields(ElementGraph.java:610)
	at cascading.flow.local.planner.LocalPlanner.buildFlow(LocalPlanner.java:95)
	... 52 more
Caused by: cascading.tuple.TupleException: field name already exists: CITY
	at cascading.tuple.Fields.copyRetain(Fields.java:1327)
	at cascading.tuple.Fields.append(Fields.java:1197)
	at cascading.pipe.Operator.resolveOutgoingSelector(Operator.java:312)
	at cascading.pipe.Each.resolveOutgoingValuesSelector(Each.java:401)
	... 56 more
```