* Fixed issue where buff effect couldn't be applied if it wasn't
stacking due to duration > 0.
* Fixed issue where foreach would throw exception due to the collection
being mutated. Use toList() to avoid this issue. A seperate
"toBeRemoved" list can be introduced if there are any memory issues.
* Added EffectStacks value to TimedBuff. This is to be able to correctly
reduce the value after a timed buff ends. (i.e. if the buff is stacked
twice, it should remove value * 2)