Yup, stupid bug catching us again.

From http://www.freertos.org/a00110.html, configTICK_RATE_HZ is the "frequency of the RTOS tick interrupt". So it's in [Hz], or [ticks/s].

From our code:
```#define portTICK_RATE_MS			( ( portTickType ) 1000 / configTICK_RATE_HZ )```

So portTICK_RATE_MS is in [ticks/s]^-1 * [1000ms/s] = [1000ms/tick]. Therefore, in order to convert from ticks to ms of time, we must multiply by portTICK_RATE_MS, or conversely in order to convert from time to ticks we need to divide by portTICK_RATE_MS.

To be honest, I'd like to see this variable renamed because it would avoid all the mistakes we have made in our code. I'm not the first one to think of this: http://sourceforge.net/tracker/?func=detail&aid=3498382&group_id=111543&atid=659636.