Honor schema in SQL query (Issue #931)

Or: Eating the same half of the pie twice

The issue was that even though the table expression has the correct schema the SQL generation was not using it.
Can we make this test consistent with the rest of the query tests? Ideally we want it to be provider agnostic and also we want to assert the SQL. Perhaps you could move it to MappingQueryTest - It currently uses Northwind but you could change the test to use "dbo", which would have the added benefit of not requiring fixture ddl.