Remove the "Close the current network" icon

[Francisco Javier Díez]

This icon, placed between the “save” and “zoom” icons, is unnecessary because there are other ways of closing a network, such as the X on the corner of its window.

Related with this, the shortcut “Ctrl+W”, which is currently assigned to “Save and reopen”, should be assigned to closing the window, as it is usual in almost all programs.

[Francisco Javier Díez]

If this proposal is implemented, the tutorial must be updated.