#471 Implemented support for activities in the catalogue.

catalogue/Catalogue.hpp

catalogue/CatalogueRetryWrapper.hpp

catalogue/CatalogueTest.cpp

catalogue/DummyCatalogue.hpp

catalogue/RdbmsCatalogue.cpp

catalogue/RdbmsCatalogue.hpp

catalogue/common_catalogue_schema.sql

common/CMakeLists.txt

common/dataStructures/RetrieveFileQueueCriteria.hpp

common/dataStructures/RetrieveRequest.hpp

common/exception/Exception.hpp

common/exception/UserError.hpp

continuousintegration/orchestration/tests/client_ar.sh

scheduler/Scheduler.cpp

xroot_plugins/XrdSsiCtaRequestMessage.cpp