"use strict" in most (if not all) our javascript

+ fix one variable leaking in global nameespace


For more about "strict mode" read [this](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions_and_function_scope/Strict_mode). 

TL DR, It's faster, less error prone and more secure.

I made it at "function level" instead of "script level" to allow concatenation with unstrict script.
But I wouldn't mind having it at script level.