EogPropertiesDialog: migrate to GAction

This patch takes care of the GAction migration in EogPropertiesDialog.
It should be considered a draft, as it is not working yet.

There is one thing to note: the action names for the dialog are now
hardcoded in EogWindow.

https://bugzilla.gnome.org/show_bug.cgi?id=741050
EogPropertiesDialog: Automatically make parent window actions available

Allows accessing the parent window's GActions via the "win" namespace.

https://bugzilla.gnome.org/show_bug.cgi?id=741050