Client can solve multiple batches of HRUs

build/includes/global/message_atoms.hpp

build/includes/summa_actor/batch_manager.hpp

build/includes/summa_actor/client.hpp

build/includes/summa_actor/summa_actor.hpp

build/includes/summa_actor/summa_client.hpp

build/includes/summa_actor/summa_server.hpp

build/makefile

build/source/actors/main.cpp

build/source/actors/summa_actor/batch_manager.cpp

build/source/actors/summa_actor/client.cpp

build/source/actors/summa_actor/summa_actor.cpp

build/source/actors/summa_actor/summa_client.cpp

build/source/actors/summa_actor/summa_server.cpp