Add null check to findByCriteria().
Overhaul the DAO tests.

This changes the DAO tests targeted at the generic methods to no longer depend
on the ApplicationDao by generating a test-only ConcreteDao (also working on
the Application model).

Also added are some more tests for the inherited methods from the abstract DAO
class.
Merge pull request #27 from marcjansen/test-overhaul

Test inherited generic DAO methods in dedicated festfile