Starting to add support for global/generic device options, e.g.
devOptions("*").  Can get, set and reset them.
Next is to add devOptions(..., inherits=TRUE) to fallback on global
options in case they are not set specifically for the queried type.
o Added support for "global" device options to fall back on if no set
  for the device type queried, e.g. devOptions("*", pointsize=14) and
  devOptions("quartz", global=TRUE)$pointsize.

STATUS: Can currently get, set and reset global options.
TODO: Add option inherits=TRUE to enable falling back to global
      options in case the option is not set for the requested device
      type.