Merge pull request #2313 from yang-g/security_context2

BUILD

Makefile

build.json

include/grpc++/auth_context.h

include/grpc++/client_context.h

include/grpc++/server_context.h

include/grpc/grpc_security.h

src/core/security/client_auth_filter.c

src/core/security/security_context.c

src/core/security/security_context.h

src/cpp/client/client_context.cc

src/cpp/common/create_auth_context.h

src/cpp/common/insecure_create_auth_context.cc

src/cpp/common/secure_auth_context.cc

src/cpp/common/secure_auth_context.h

src/cpp/common/secure_create_auth_context.cc

src/cpp/server/server.cc

src/cpp/server/server_context.cc

...2end/tests/request_response_with_payload_and_call_creds.c

test/core/security/auth_context_test.c