Add getKey test to program test
Refactor program getKey test

Refactors the program getKey test to use a new AppEngineTest base
class.

After this commit, new test classes should inherit from AppEngineTest
when they require the use of App Engine SDKs, like the
PersistenceManager.
Add getKey test for the student entity
Test UserCreator
Test Authenticator
Test ProgramCreator
Test ProgramFinder
Test StudentFinder
Test StudentCreator
Test StudentEnroller
Test ProgramViewer
Test ProgramIncomeViewer
Merge pull request #25 from fantastic-five/more_tests

Test use cases