This removes the `pb` based progress bar for the transfer queue and add
a simpler custom bar. pb really wants to know total counts and byte
sizes up front but when doing batches of n we would prefer to not know
that. This is due to the fact that the batcher will block until it is
drained instead of processing all pointers and storing them in memory
while transfer operations run. This also clarifies when files are
skipped because the server already has them. Progress output here
contains the number of finished transfers/bytes, the number of
transfers/bytes currently in the queue, and the number of files skipped,
if any.
