[evince] PDF metadata editing UX

[Jakub Kucharski <jakubkucharski97 gmail com>]

Hello, everyone!

I've just sent my patches[1] which enable the user to edit PDF
metadata. Since it introduces new methods of interaction (I've tried to
mimic other GNOME software), it should probably be reviewed by a UX
designer. So if anyone has a little bit of time, feel free to evaluate
it.

Oh, and remember to read my first comment[2] about the patches.

Cheers,
Jakub

[1] https://bugzilla.gnome.org/show_bug.cgi?id=684851
[2] https://bugzilla.gnome.org/show_bug.cgi?id=684851#c1