Merge pull request #6373 from y-zeng/server-builder-plugin

BUILD

Makefile

build.yaml

include/grpc++/impl/server_builder_option.h

include/grpc++/impl/server_builder_plugin.h

include/grpc++/impl/server_initializer.h

include/grpc++/server.h

include/grpc++/server_builder.h

src/cpp/server/server.cc

src/cpp/server/server_builder.cc

test/cpp/end2end/async_end2end_test.cc

test/cpp/end2end/server_builder_plugin_test.cc

tools/doxygen/Doxyfile.c++

tools/doxygen/Doxyfile.c++.internal

tools/run_tests/sources_and_headers.json

tools/run_tests/tests.json

vsprojects/vcxproj/grpc++/grpc++.vcxproj

vsprojects/vcxproj/grpc++/grpc++.vcxproj.filters

vsprojects/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj

...s/vcxproj/grpc++_unsecure/grpc++_unsecure.vcxproj.filters