Merge with head and resolve conflict

.gitignore

BUILD

Makefile

README.md

build.json

doc/connection-backoff.md

doc/interop-test-descriptions.md

gRPC.podspec

include/grpc++/auth_context.h

include/grpc++/auth_property_iterator.h

include/grpc++/completion_queue.h

include/grpc++/fixed_size_thread_pool.h

include/grpc++/impl/call.h

include/grpc++/server_context.h

include/grpc++/stream.h

include/grpc++/thread_pool_interface.h

include/grpc/grpc.h

include/grpc/support/port_platform.h

include/grpc/support/time.h

include/grpc/support/useful.h