Moved castor::tape::aggregator::SmartFd and

castor::tape::aggregator::SmartFdList to the castor::tape::utils package.
This has been done to prepare for the addition of the yet to be developed
castor::tape::utils::SmartFILEPtr which will be required to implement the safe
closure of the TPCONFIG file using the "resource acquisition is resource
allocation" approach.