* Popup menus now remember the last clicked item again.
* Modifier and File Format menus are now organized in multiple
columns with categories.
* Hook, explode, uv project modifiers have all their buttons
again with the relevant operators implemented.
* Modifiers that can't be added by the user, or don't work on
curves for example, are not in the menu anymore.
* Fix search menu overlapping buttons when near the bottom of
the screen.
* Fix uv layers search menu not working in some modifiers.
* Cleanup popup menu code a bit, layout engine is used in more
cases now instead of ugly position calculation code.
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