context menu enhancement

[knilink]

1. The context menu should preserve it state after being closed. Such as if I active and expand a category, it should stay active if I trigger the context menu next time.
2. Hide the triangle if the menu item has no children.
3. Disable or increase the speed of the animation. Just feel too slow to me.
4. Not necessary to have a default item, could be like following: [expand/collapse] → ▷ string ← [default string input] .....................................└ textarea ←[textarea]

[knilink]

Usage:

• Click on the top "Menu" item to expand/collapse all categories
• Click on the title of a category to expand/collapse the categories
• Click on outside of the menu to dismiss the menu