TODO
----
* Fix gettext issues so I don't have to use a special
  #define dg_(s)  dgettext (PACKAGE, s)
  Somehow PACKAGE_GETTEXT is set to something else ...
* [DONE] unload unused plugins 
* plugin library
  - with API docs
* smarter resize/move
  - [DONE] popup arrow direction
  - [DONE] keep panel on same x/y alignment
  - [DONE] save 'centered' state to better keep the panel aligned?
* [DONE] use icon theme spec
* [DONE] Move the exec_cmd stuff to libxfce4util/libxfcegui4
* [DONE] Move to glib xml parsing. More work, but more speed / 
  reduced memory usage
* multiple panels
  - Most settings should become per panel
  - multiscreen
  - taskbar == panel instance?
* beter DND support
  - add/remove
  - move
* gtk widgets (panel, controls)
  - include move handles (steal code form GtkHandlebox)
  - use properties and signals for settings
  - perhaps use interfaces or derived widgets for controls

Ideas
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* plugins:
  - dockapps support
* 2 plugins side by side 
   (like systembuttons)
* change icon themes to use a mapping between categories and icon names that
  can be looked up using the icon theme spec?
  e.g.:
  [Xfce panel icon theme]
  network=gnome-network
  file1=xdg:folder
  ...