Add a studio 'say' block that accepts a time input in seconds

Goal: for playlab counting levels, sprites should be able to count 1..100 without taking minutes to complete.

<img src="https://cloud.githubusercontent.com/assets/413693/4946726/22c8d1f2-6618-11e4-8fae-17db53171357.png" width="400">

I wonder if this is going to be difficult to translate properly without context. I wonder if we would be better of having the full phrase with params, something like
"numBlocksNeeded": "This puzzle can be solved with %1 blocks.  You used %2.",