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 checks the checksum of the streamed encrypted data against the
checksum of the encrypted object returned from the remote and returns
an error if it is different.
* Implement about for:
* local, crypt, cache, drive, swift, hubic, onedrive, pcloud, dropbox
* Implement `--json` and `---full` flag for `rclone about`
* change About interface to return a Usage structure
* Remove operations.About as it is too thin an interface
* Implement Integration test
Relates to #1138 and #1564
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.
