Some refactoring of end2end test.
Added discrimination analysis to end2end test.
Implemented DiscriminationAnalysis.
Added discrimination analysis to StandardAgentContainer.
Implemented discrimination analysis in StaticallyPairingInteractor.
Added DiscriminationGroup to encapsulate list of objects for a single
discrimination game.
Listener agent requests object description from speaker, and gets
discrimination score from interpretation.
Interpretation calculates discrimination score based on groups of game
objects and associated descriptions of target objects from other agent.