[EOS-CTA] Converts error responses into exceptions on client side

cmdline/EosCtaApi.h

cmdline/EosCtaStub.cpp

eos/messages/eos_messages.proto

xroot_plugins/XrdSsiCtaRequestProc.cpp

xroot_plugins/XrdSsiCtaService.h

xroot_plugins/XrdSsiCtaServiceProvider.cpp

xroot_ssi_pb/XrdSsiPbAlert.hpp

xroot_ssi_pb/XrdSsiPbDebug.hpp

xroot_ssi_pb/XrdSsiPbException.hpp

xroot_ssi_pb/XrdSsiPbRequest.hpp

xroot_ssi_pb/XrdSsiPbRequestProc.hpp

xroot_ssi_pb/XrdSsiPbServiceClientSide.hpp