cta::client::MockAPI now implements storage class methods

libs/CMakeLists.txt

libs/ctaclient/CMakeLists.txt

libs/ctaclient/cta/client/API.cpp

libs/ctaclient/cta/client/API.hpp

libs/ctaclient/cta/client/CMakeLists.txt

libs/ctaclient/cta/client/MockAPI.cpp

libs/ctaclient/cta/client/MockAPI.hpp

libs/ctaclient/cta/client/MockAPITest.cpp

libs/ctacommon/CMakeLists.txt

libs/ctacommon/cta/StorageClass.cpp

libs/ctacommon/cta/StorageClass.hpp

libs/ctacommon/cta/StorageClassList.hpp

libs/ctacommon/cta/exception/Exception.cpp

libs/ctacommon/cta/exception/Exception.hpp

libs/ctacommon/cta/filesystem/DirectoryConstIterator.cpp

libs/ctacommon/cta/filesystem/DirectoryConstIterator.hpp

libs/ctacommon/cta/filesystem/DirectoryEntry.cpp

libs/ctacommon/cta/filesystem/DirectoryEntry.hpp

unit_tests/CMakeLists.txt