[v6r11] SSHTorque CE fix and others

FIX: SSHTorqueComputingElement - use SSHUser instead of BatchUser option to pass to qselect query
BUGFIX: ReplicateAndRegister - do not ask SE with explicit SRM2 protocol
FIX: RequestTask - always execute operations with owner proxy
BUGFIX: DataManager - bug fix in __removeReplica()
NEW: added returnSingleResult() gereric utility by moving it from Resources/Utils module