fix affect_allies can have 3 value true,false and noexistent

when abilities don't have affect_allies implemented, then onlyunit same side are affected, if affect_allies=yes, unit of allied side inclus and if falsethen none unit allied or same side are affected.

data/schema/filters/abilities.cfg

@@ -14,7 +14,7 @@
 	{SIMPLE_KEY divide s_real_range_list}
 	{SIMPLE_KEY affect_adjacent s_bool}
 	{SIMPLE_KEY affect_self s_bool}
-	{SIMPLE_KEY affect_allies s_bool}
+	{DEFAULT_KEY affect_allies affect_allies_filter empty}
 	{SIMPLE_KEY affect_enemies s_bool}
 	{DEFAULT_KEY type_value value_type empty}
 	{FILTER_BOOLEAN_OPS abilities}

data/schema/game_config.cfg

@@ -44,6 +44,10 @@
         name="value_type"
         value="empty|value|add|sub|multiply|divide"
     [/type]
+    [type]
+        name="affect_allies_filter"
+        value="empty|yes|no"
+    [/type]
     [type]
         name="addon_type"
         value="sp|mp|hybrid"

src/units/unit.cpp

@@ -1457,8 +1457,13 @@ static bool matches_ability_filter(const config & cfg, const std::string& tag_na
 	if(!bool_matches_if_present(filter, cfg, "affect_self", true))
 		return false;
 
-	if(!bool_matches_if_present(filter, cfg, "affect_allies", true))
+	if(!filter["affect_allies"].empty() && !cfg["affect_allies"].empty()){
+		if(!bool_matches_if_present(filter, cfg, "affect_allies", true)){
+			return false;
+		}
+	} else if(!filter["affect_allies"].empty() && filter["affect_allies"].str() != "empty"){
 		return false;
+	}
 
 	if(!bool_matches_if_present(filter, cfg, "affect_enemies", false))
 		return false;