Revert "Add back eog_window_open_editor as we might still need it"

This reverts commit 72253fdf400247092fd6ed613e95f6b023330dc8.
Revert "Remove the GtkMenuBar"

This reverts commit 3d0405be352fa13e7021d19d1ead1375140b41c3.
Revert "Remove all other references to the toolbar"

This reverts commit 6df4284cda1954e4192d387a676df1fc50730647.
Revert "src: remove all code related to EggEditableToolbar"

This reverts commit 36ff7907cfc0697266fbf43ba0bd55eecb4bac7c.
Revert "eog-window.c: GtkAction -> GAction"

This reverts commit 8b1fc17689d3a73abcabfb55de4721c1f7eac22b.
This was not meant to be pushed to master yet.