ok, let's do this slightl more correctly, featuring:

- a dbus appropraite callback (e.g. it shouldn't pop up a UI for the user to interact with.)
- a menu instead of a dialog

next up: getting other appropriate apps in the list via dbus so we can email images. servicemenus seem the natural way to go here but they need some work before they can be used here. ("Rotate image" is probably stupid to show in this menu, but "Email image" isn't)