panel: menu: rejig menu items

[trigg]

• remove the extra button
• overlay as top-layer inside flowboxchild
• • box
• • • image = icon
• • • label = name
• • menubutton = extra actions
• menubutton is hidden if no extra actions exist

[trigg]

This will cause a change to wiki, naturally

Menu (Popup)

| - popover .menu-popover
  | - box no-class
    | - scrolledwindow .category-list-scroll
      | - box .category-list
        | + button .app-category (One for each category)
          | - box no-class
            | - image no-class
            | - label no-class
    | - scrolledwindow .app-list-scroll
      | - box no-class
        | - flowbox .app-list
          | + flowboxchild (One each for every filtered app launcher)
            | - overlay .app-button
              | - box no-class
                | - image .default-icon
                | - label no-class
            | - menubutton .app-button-extras
    | - entry .app-search
    | - box no-class
      | - button no-class (logout)