Popup crashes when used on a regular array

[orels1]

If you try to add a popup to a regular array - it will crash due to not being suited for that (the Property Drawer gets passed the data SerializedProperty` and it just crashes and burns)

[Popup("Handler")]
public string[] stuff;

Need to handle it in the UTEditor code

• Avoid nested properties in popups
• Handle the popups directly in the RenderArray code same way as the RenderStackedArray does it
• Refactor the popup lookups to a UTUtils function
• Documented the updated logic