eliminate WriteDg()

	modified:   src/bruce/input_dg/any_partition/v0/v0_input_dg.test.cc
	deleted:    src/bruce/input_dg/any_partition/v0/v0_write_dg.cc
	deleted:    src/bruce/input_dg/any_partition/v0/v0_write_dg.h
	modified:   src/bruce/input_dg/partition_key/v0/v0_input_dg.test.cc
	deleted:    src/bruce/input_dg/partition_key/v0/v0_write_dg.cc
	deleted:    src/bruce/input_dg/partition_key/v0/v0_write_dg.h
	modified:   src/bruce/simple_client/simple_bruce_client.cc