Prepares resolved data.frame for ggplot. Appends
units to label using append_units
(passing style = 'plotmath' if parse
is true, else style = 'plain').
Enforces classes 'decorated','resolved', and 'ggready'.
Unlike ggready.decorated, the
method for class resolved does NOT call resolve(),
and so does not second-guess any particular
resolutions you may have already made.