Add Options dialog which allows users to set more options than current dialog.
The dialog reads printer's PPD file and add its options to the dialog together
with some preselected IPP options (#678637).
All operations in the dialog are asynchronous.
During implementation of this, the option for setting allowed users was removed
because this is not suitable for this panel (the option is intended for
administrators).
This commit adds popup window which when activated allows
user to select PPD from local database of installed PPDs,
select directly PPD from filesystem or select one from 3
recommended PPDs (#678637).
The popup is activated by clicking on model field (the panel
has to be unlocked). It starts to search for the best PPDs
available immediately after its popup.
All operations are asynchronous.
The dialog is able to add printers discovered by cupsGetDevices().
It can also add printers from a remote CUPS server by typing
its address and selecting printer we want to add (#640734).
