Add advanced randomizer

Hello,

The current randomizer only allow to rand between 4 values. Here an advanced randomizer.

It send a random value between + and - value when the 'reset' node receive a signal.

Here a screen where + and - are connected to a counter, and the 'reset' node is connected to a button.
![image](https://cloud.githubusercontent.com/assets/339611/3628847/dd8b3674-0e98-11e4-9fbd-0ce88998fb67.png)