Before this change backend types were printing incorrectly as the name
of the type, not what was defined by the Type() method.
This was not working due to not calling the Type() method. However
this needed to be defined on a non-pointer type due to the way the
options are handled.
This is possible now that we no longer support go1.12 and brings
rclone into line with standard practices in the Go world.
This also removes errors.New and errors.Errorf from lib/errors and
prefers the stdlib errors package over lib/errors.
