Propagated references to the watchdog to disk and tape threads and tasks.
Added a maps for storing the count of all errors that occured during the session.
Added propagation of the counts to the initial process.
Added error reporting in disk and tapes threads and tasks by using a string marker
allowing to know which part went wrong in high level exception. Exceptions then
bumps up the count in the watchdog (synchronously), and the watchdog sends the
new count to the initial thread later (in the watchdog's thread).
Plus some missing logs fixed when an exception is thrown in a disk write task.

Added interface to reference the recall watchdog to the recall disk thread pool.
Next: Do same for migration. Actually store the reference. Add new error map storing in watchdog. Add error reporting in tape and disk threads.

WIP: Added missing file ID for disk write thread. Added missing error log when an exception is thrown in a disk write task.

WIP: switching to CASTOR-4839 tapeserverd: task injector should decide on closing the session earlier

WIP. Next: log unmount errors (in the RAII)

Finished error counting in data threads.