Fix schedule sorter

[paul]

When OVA "sorts" the ad schedule in AdsConfigGroup.as3 - the sorting is done into pre, mid and post buckets, but this is flawed if pre, mids and posts are applied differently across multiple ad slots.

Confirm, and if required, improve the algorithm to take this into account.

See step 2 in:

public function set schedule(schedule:Array):void {
}

For the code.