Create a custom Print dialog

[D0J0P]

From #125. Although it wasn't approved when brought up about Photos' same print screen in #515, thought I'd bring it up for Epiphany. So far, those are the only 2 apps shipped with elementary that have print screen taken from GTK/Gnome.

[janxkoci]

This print dialog is also in Evince. I didn't even know that elementary has it's own print dialog, as I only use it for web (Epiphany), PDFs (Evince) and Office (LibreOffice has it's own dialog).

I will have to check this when I come home as I have no idea how the elementary version looks like 😃

EDIT: from the second bug you linked it seems there is no elementary version 😞

[danirabbit]

I'm going to move this to the portals repo as a wishlist item there. All apps will have to go through the Print portal eventually. For now I think that uses the Gtk dialog (which all our apps currently use). But that's the only sane way we could implement a custom Print dialog.

So for clarity, please don't open issues about a print dialog on every repo. If we were to supply a custom print dialog, it would be solved once in the portals repo

[ryonakano]

I started working on this in the ryonakano/print-portal branch, using Print Portal in the GTK one as a reference: