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 checked with @tanyaparker, she has plans to improve i18n for these short strings but suggested doing it this way for now.  For loops are done the same way: in `count with <variable> from <#> to <#> by <#>` each token is localized separately.