[first draft] enhanced version of SqlPredicateTest

Missing features:
- fully configurable customPredicate
- needs more types of customPredicate

Waiting your review.
there is a lot of repetition of Employe implementation logic,  we could have a EmployeImpl calss implementing Employee,  and DataSerializableEmployee extending EmployeImpl implementing DataSerializable.  same for IdentifiedDataSerializableEmployee,  SerializableEmployee,  PortableEmployee.