use the ubuntu launcher API to populate the correct icon

[totaam]

With unity, the icon shown in the "dock" area is not the one we specify for the tray icon, but it should probably be.

Problems:

• this is an Ubuntu / Unity thing only (and they've caused us enough pain already)
• the Python Launcher API is gtk3 only... (gobject introspection) so we would need some simple ctypes wrappers (or Cython, whatever is easiest)
• the icons we have are probably too low-res to look good in the dock (that's not insurmountable)

See also: #508 and #228

[totaam]

Scheduling for this release, together with #508 and #476.

Links:

• http://askubuntu.com/questions/169582/how-to-display-in-unity-an-exported-gmenu-in-dbus
• indicator-appmenu
• https://launchpad.net/libdbusmenu (totally useless page - complete waste of time: lots of links, but not one bit of documentation)
• dbus python qt example (not so different from plain python)
• https://launchpad.net/plasma-widget-menubar
• How to add support for the global menu to a python non-gtk, non-qt app?
• How to display in Unity an exported GMenu in DBus?

[totaam]

I thought it should be relatively easy to query these menus via dbus, there is an "appmenu registrar" service after all and the interface looks sane, but querying it the path always comes up as "/".
Instead, it looks like we need to look for _UNITY_OBJECT_PATH,

And whilst we're dealing with this, it might make sense to forward appindicators: How does one find out which application is associated with an indicator icon?.

Not for this release.

[totaam]

Hopefully Ubuntu will completely drop Unity and its APIs then we can focus on just one (gnome's): #476.