Notification spec issue: Ability to assign an icon *and* an image to a notification

[Aurélien Gâteau]

Here is another suggestion, which would be more compatible with
the existing spec:

- Introduce the image_data hint, following the iiibiiay (or iiay ?) format

- State that the icon_data hint must still be supported, but is
considered obsolete

- Introduce the image_path hint, following the same convention as the
app_icon hint (==either URI to image or icon name following fdo icon
naming spec)

- State that an implementation which displays only one image must
consider image fields in this order: image_data, image_path, app_icon,
icon_data

- State that an implementation which can display an app icon and an
image must consider image fields in this order: image_data,
image_path, icon_data

- Introduce a new method to check which version of the spec is
implemented by the server:
  org.freedesktop.Notifications.GetSpecVersion(out INT32 major,
                                               out INT32 minor)

What do you think about this?

Aurélien