This reports the amount of data transferred and the throughput (averaged
over 60 seconds) to the master daemon. While not yet fully implemented,
once the export scripts report the expected data size, we can even provide
an ETA and percentage.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>

The import/export daemon code is already large. Moving some code
to a separate module will make it smaller and easier to test.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>