The sftp library delivers the attributes of the symlink rather than
the object pointed to in directory listings, however when we use Stat
from the library it points to the objects.
Previous to this fix this caused items pointed to by symlinks to be
unusable.
After the fix both symlinked files and directories work as expected.
A Range request can never request 0 bytes however this change was made
to make a clearer signal that the limit means read to the end.
Add test and more documentation and fixup uses
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.
