[Feature Request] A `ChangeProperty` Method for Lua Storyboard Elements

Something like this will really be a huge improvement for storyboards. As of now you can't really change the Z ordering or Text of a ``StoryboardText`` and so on during the runtime of a storyboard.

interface for it will probably be like

``ChangeProperty("key", time, value)``


```lua
local text_spr = StoryboardText()
text_spr:ChangeProperty("text", 1400, "new text!")
```