Report overall transfer progress.

Currently the log receives updates for every 20% progress step per file. It would be very useful (also for the tray app #2 (closed)) to report the overall progress instead.

added Doing and removed To Do labels

mentioned in commit a651bafb

closed via commit 3a4d0abf

removed Doing label

mentioned in commit 07325fec

mentioned in commit cdc0e012

mentioned in commit ae06f63d

added enhancement label