Merge branch 'eos_cta'

.gitlab-ci.yml

.gitmodules

CMakeLists.txt

cmake/FindProtobuf3.cmake

cmdline/CMakeLists.txt

cmdline/CtaAdminCmdParse.hpp

cmdline/EosCtaStub.cpp

eos_cta/CMakeLists.txt

xroot_plugins/CMakeLists.txt

xroot_plugins/XrdCtaArchiveFileLs.hpp

xroot_plugins/XrdSsiCtaRequestMessage.hpp

xroot_plugins/XrdSsiCtaServiceProvider.cpp

xroot_plugins/messages/CtaFrontendApi.hpp

xroot_plugins/messages/cta_admin.proto

xroot_plugins/messages/cta_common.proto

xroot_plugins/messages/cta_eos.proto

xroot_plugins/messages/cta_frontend.proto

xroot_ssi_pb/README.md

xroot_ssi_pb/XrdSsiPbAlert.hpp

xroot_ssi_pb/XrdSsiPbDebug.hpp