X2Effect_Persistent::GetAttackingDamageModifier() does not get the damage effect during damage preview

[Iridar]

This means that persistent effects that add contextual damage bonuses depending on the damage effect properties do not actually get said context until the damage effect will be applied, so they cannot properly display their damage bonuses during damage preview.

This, for example, causes the bug described in #612.

Solution: add a GetAttackingDamageModifier_CH() method that will have the damage effect passed to it as an argument.

[Iridar]

Something weird, getting the following errors in the Launch log now:

[0006.83] Error: (AddNetObject) Objects Function XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH and IntProperty XComGame.X2Effect_Persistent:GetDefendingDamageModifier.ReturnValue have duplicate NetIndex 51097
[0006.83] Error: (AddNetObject) Objects ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.EffectState and Function XComGame.X2Effect_Persistent:GetAttackingDamageModifier have duplicate NetIndex 51096
[0006.83] Error: (AddNetObject) Objects ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.Attacker and ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier.EffectState have duplicate NetIndex 51095
[0006.84] Error: (AddNetObject) Objects InterfaceProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.TargetDamageable and ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier.Attacker have duplicate NetIndex 51094
[0006.84] Error: (AddNetObject) Objects ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.AbilityState and InterfaceProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier.TargetDamageable have duplicate NetIndex 51093
[0006.84] Error: (AddNetObject) Objects StructProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.AppliedData and ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier.AbilityState have duplicate NetIndex 51092
[0006.84] Error: (AddNetObject) Objects IntProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.CurrentDamage and StructProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier.AppliedData have duplicate NetIndex 51091
[0006.84] Error: (AddNetObject) Objects ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.WeaponDamageEffect and IntProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier.CurrentDamage have duplicate NetIndex 51090
[0006.84] Error: (AddNetObject) Objects ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.NewGameState and ObjectProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier.NewGameState have duplicate NetIndex 51089
[0006.84] Error: (AddNetObject) Objects IntProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier_CH.ReturnValue and IntProperty XComGame.X2Effect_Persistent:GetAttackingDamageModifier.ReturnValue have duplicate NetIndex 51088