...before moving to first item of next job queue queue, which requires
one additional call to operator++

Summary now includes all tapepools, including those with no queued jobs
(previously we only showed a summary of queues containing jobs)

Conflicts:
	scheduler/OStoreDB/OStoreDB.hpp
	xroot_plugins/XrdSsiCtaRequestMessage.cpp

Better to have all formatting on the client side, so we format the
header and the reponse values in the same place. (Also no need to
send this data over the wire as it's always the same).

PB now accommodates "lpa" and "lpr" responses as well as "af ls"

The test relies on this order.

The new default is 10 for unit tests.
The number is set by the frontend, which is the only process where it matters. The default
in the configuration file is set to 500 for CI tests.

I tried putting this through the Scheduler, but as getArchiveQueueItor
returns an object of type QueueItor, I would have to expose the itor
class everywhere that the Scheduler is used. As this would not be
easy to maintain, I backtracked and instead call the method directly
on the OStoreDB object.

The requeust is now created first so the data is safe before returning to the caller.
Also improved the timing logging.

This version is not data safe as the request is created late, right after
referencing the job to the queue.

Permits async/streaming access to job queues

It's only TapePool in the case of archives, retrieves are filtered on
vid

The size is set to 500 to allow unit tests to pass.
Next steps are: port the mechanism to retrieve, and make the thread pool size configurable.

The top half goes as far as when the request is safe in the object store.
At that point, the bottom half is launched in a new thread, and success is returned
the called. This will enable lower latency for the users while retaining
the same data safety.

This version is experimental aas it spans an undetermined number of threads. A more controlled
version with a work queue should be implenented on the long run.

All new code is now in QueueItor.hpp

For async/streaming access to the contents of archive and retrieve
queues.