ENH: Submit parameter "load"

pb/comm.proto

python/loom/client/client.py

src/server/clientconn.cpp

src/server/compstate.cpp

src/server/compstate.h

src/server/taskmanager.cpp

src/server/taskmanager.h

tests/client/loomenv.py

tests/client/test_checkpoint.py

tests/cpp/test_scheduler.cpp