Make expand all / collapse all buttons in scene editor area

[Zeffuro]

Would be nice, also an option to remember what was expended in the previous scene would be nice, if I for example like to see all actors it would save a click per scene :)

• Remembering expanded nodes when switching scenes
• Expand all / collapse all

[agrande]

Reason I didn't do this so far is because I was worried having all nodes expanded at once would take a performance hit (many variables to observe that change every frame).

Also, at the beginning the scene editor was not too stable, so it would have caused more crashes.
Maybe it's not so much a problem anymore , I should test that out.

Also, I'm trying to avoid adding complexity by supporting too many features at this early stage.

Remembering the expanded node though sounds like something important, but that one should be easier.

[agrande]

Maybe those 2 tasks should be 2 separate issues.