let new caption inset be a collapsable one

[Uwe Stöhr]

I'm now workig with the new caption inset while writing a paper with many floats. In my opinion it 
would be a bit better usable when it can be collapsed. Do others agree? If yes and if it's not too 
much work, it would be an impovement if this is implemented for LyX 1.5.

regards Uwe