Define Perk Volley aliases to use with AnimNotify_FireWeaponVolley

[robojumper]

AnimNotify_FireWeaponVolley can trigger perk volleys. Those don't fire the currently equipped weapon, but take it from an XComPerkContent that is eligible for an ability of the specified name.

The relevant lines are in XGUnitNativeBase

if ((CurrentPerkAction != none) && (CurrentPerkAction.GetAbilityName() == Notify.PerkAbilityName))

Which should be easy to adapt for an alias list, and X2UnifiedProjectile

kContent = XComUnitPawn( SourceWeapon.m_kPawn ).GetPerkContent( VolleyNotify.PerkAbilityName );

which might be more tricky. It needs to check all the aliases until it finds one. GetPerkContent should not be modified, it's called by other Actions too.