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
Previously this was reading a stale hash from the object leading to
broken integration tests.
This fixes these integration tests TestSyncDoesntUpdateModtime,
TestSyncAfterChangingFilesSizeOnly, TestSyncAfterChangingContentsOnly,
TestSyncWithUpdateOlder, TestSyncUTFNorm.
* Fix errcheck and golint warnings
* Remove unused constants and fix comments
* Parse error responses properly
* Fix Open with RangeOption
* Fix Move, Copy and DirMove
* Implement DirCacheFlush
* Check interfaces are correct
* Remove debugs and update overview
* Correct feature flags
* Pare replacement characters down to the minimum set
* Add to the integration tests
* Add Mkdir, Rmdir, Purge, Delete, SetModTime, Copy, Move, DirMove
* Update file size after upload
* Add Open seek
* Set private permission for new folder and uploaded file
* Add docs
* Update List function
* Fix UserSessionInfo struct
* Fix socket leaks
* Don’t close resp.Body in Open method
* Get hash when listing files
