--max-backlog controls the queue length.
Add statistics for the check/upload/rename queues.
This means that checking can complete before the uploads which will
give rclone the ability to show exactly what is outstanding.
Unfortunately this commit attempts to create every directory rather
than just the empty ones, so will need re-working.
Removing this feature for the 1.41 release
This reverts commit 0daced29db.
The purpose of this is to make it easier to maintain and eventually to
allow the rclone backends to be re-used in other projects without
having to use the rclone configuration system.
The new code layout is documented in CONTRIBUTING.
