This unifies the 3 methods of reading config
* command line
* environment variable
* config file
And allows them all to be configured in all places. This is done by
making the []fs.Option in the backend registration be the master
source of what the backend options are.
The backend changes are:
* Use the new configmap.Mapper parameter
* Use configstruct to parse it into an Options struct
* Add all config to []fs.Option including defaults and help
* Remove all uses of pflag
* Remove all uses of config.FileGet
This removes the old system of part accounting and replaces it with a
system of popping off the accounting reader and wrapping up new ones
as necessary.
This makes it much easier to carry the context down the chain of
wrapped readers and get the limiting as near as possible to the
output. This makes the accounting more accurate and the bandwidth
limiting smoother.
Fixes#2029 and Fixes#1443
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.
