This almost 100% backwards compatible. The only difference being that
in the rc options/get output CutoffMode, LogLevel, TerminalColorMode
will be output as strings instead of integers. This is a lot more
convenient for the user. They still accept integer inputs though so
the fallout from this should be minimal.
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.
Before this change options were read and set in native format. This
means for example nanoseconds for durations or an integer for
enumerated types, which isn't very convenient for humans.
This change enables these types to be set with a string with the
syntax as used in the command line instead, so `"10s"` rather than
`10000000000` or `"DEBUG"` rather than `8` for log level.
