Completed the garbage collection unit test.

objectstore/Agent.cpp

objectstore/Agent.hpp

objectstore/BackendTest.cpp

objectstore/FIFO.cpp

objectstore/FIFO.hpp

objectstore/GarbageCollector.cpp

objectstore/GarbageCollectorTest.cpp

objectstore/GenericObject.hpp

objectstore/ProtcolBuffersAlgorithms.hpp

objectstore/ProtocolBuffersAlgorithms.cpp