Parse options job-sheets, job-hold-until and sides correctly.
Add get_lpoption_name() for translation of lpoption names to
gtk option names. Usable for options which values don't need
conversion (e.g. number-up, number-up-layout, job-billing
and job-priority).
Rename array option_names to ppd_option_names to reflect its
purpose better. Rename get_option_name() to get_ppd_option_name()
because of the same reason.