Temporarily added the txtype parameter to the signature block. This part should be improved to support the optional castor.pool parameter, instead of just concatenating the (repeated) values

for a d2d transfer. The way the tokens are concatenated is important and should follow
the order specified in xrootd/XrdxCastor2Acc.cpp:BuildToken.

Dropped Client.secure from the transfers as it's never used - RFIO is unsecure, GFTP and XROOT are secure in all cases

Renamed castor2fs to castor for the URL parameters and added a pfn2 parameter to URLs for disk-to-disk copies

        "castor2fs." to "castor."

        a random ones using uuid.

        also include this new information when computing the signature of each
        transfer. The transfer type for client requests is "user".

Implemented the diskmanager side of the OPEN call from movers, to be used by xroot for user transfers as well as to notify internal (in particular tape) transfers

Dropped listing of tape transfers: this is going to be replaced by querying the xroot server for the ongoing transfers

Reworked the physical layout of the SubRequest table: now it is partitioned by 5 groups of statuses + subpartitioned by hash(id) to spread the load

Tests using writetp were no longer passing due to the new
"terminate session early" logic of the tapeserverd daemon.
The daemon was askng for a minimum batch of 250 files. The
writetp command only ever gave one file per batch of work.

An attempt to introduce proper for protobuf dependencies as the previous solution led to systematic recompilation.

errors for a non-crashing session can also be recorded as a failures in the
tape log.