[implemented] Track merciless resolve stacks as a buff

[Letho]

Hey Chip,

now that the five stacks from merciless resolve (nightblade ability) do not reset when the buff falls off/is recast, it would make sense to let players track the stacks. Could it be added back to buffs so that EVENT_EFFECT_CHANGED communicates it? Currently it is only possible to make addons 'guess' the stacks by tracking each hit done by a light attack.

Cheers