Make batch operations work with joins or throw proper exception

[MikaelEliasson]

Right now a call like this:

EFBatchOperation.For(db, db.InvoicePayments).Where(x => x.Invoice.OrgNumber == c.OrgNumber).Delete();

Result in exception about a missing alias because the alias is not properly defined when grabbing the WHERE part from the query.

Investigate if this can be fixed or provide a better exception.