Added the first version of the specification of the Catalogue::getTapeFilesForRepack() method - there's no implementation yet

Added MEDIA_TYPE and VENDOR columns to TAPE table and upgraded xrootd-ssi-protobuf-interface to v0.29

The catalogue can receive polymorphic items as input for recording.
The strict sequencing of fSeqs is still enforced.
Currently, 2 items types are recorded: files and placehoders.
Files are recorded to the tape catalogue, while place holders are not,
but they are used to enforce the fSeq sequencing.

Done

Added CatalogueRetryWrapper.hpp