Shadowstrike changes

In current version, the unseen crit bonus for Shadowstrike effect is not in effect because of a bug. This patch will fix this problem.

However, even after the fix, with the current setting of Shadowstrike, it will not trigger for any damage with __project_source. That includes all projectiles, so rogue's signature throwing knives will never get Shadowstrike bonus.

Since Shadowstrike is no_npc_use now, we won't need to worry about its side effect on enemies, and here we can have an review about its position in rogue/shadowblade build. Considering breaking stealth will give you generic combat_critical_power that will apply to any damage, it iscounter-intuitive that manually break stealth may give a better bonus on your alpha strike. Maybe we could just relax that restrictions for better synergism with throwing knife, or maybe choose not to do this, since it's already a skill that won't break stealth and you have gained the guranteed crit for free.

There is also a legacy problem in orcs/superload/mod/class/interface/Combat.lua:130 that SHADOWSTRIKE will give you some crit_power_add, which would be duplicated with the code in damage_types.lua