1 - non-attached annotation => suggest a derived filename for save-as
3 - prefs file, save prefs
6 - flatten (incl undo/redo...) - enabled only if nlayers>1
7 - bg: apply to all pages
10 - move selection to another page by drag-drop
11 (should apply to vertspacer when origin moves to another page,
12 but in the up direction only do so when all the stuff fits on prev page)
14 - text tool, font chooser, default font
15 - color chooser (papercolor, pen color); maybe more default colors
16 - printing: print-to-PDF? (with & without pdf background to merge)
17 opacity issue for highlighter strokes (maybe print them below ?)
18 save gnome printer settings (throughout a session, and on disk)
19 (maybe a separate config file .xournal/gnome-print-settings)
21 - file print-options, own print-to-ps/pdf
23 - pressure sensitivity
24 - insert images (screen capture or from file), not as full-page backgrounds
25 - more pen/highlighter shapes (chisel)
26 - convert to/from Jarnal format
27 - recalibration upon screen resize / compensation for miscalibration