List feats in the order that they're added

Feats are collected in character.py first by race, then by background,
and finally by class. And within each of these, they're collected by
level. That yields a very nice order that lends itself for some
additional subheadings. In order to do so change "fts" to list instead
of set, to preserve order.

dungeonsheets/character.py

@@ -450,7 +450,7 @@ def other_weapon_proficiencies_text(self):
 
     @property
     def features(self):
-        fts = set(self.custom_features)
+        fts = list(self.custom_features)
         fighting_style_defined = False
         set_of_fighting_styles = {
             "Fighting Style (Archery)",
@@ -468,7 +468,8 @@ def features(self):
         if not self.has_class:
             return fts
         for c in self.class_list:
-            fts |= set(c.features)
+            for item in list(c.features):
+                fts.append(item)
             for feature in fts:
                 if (
                     fighting_style_defined
@@ -478,15 +479,17 @@ def features(self):
                     fts.remove(temp_feature)
                     break
         if self.race is not None:
-            fts |= set(getattr(self.race, "features", ()))
+            for item in getattr(self.race, "features", ()):
+                fts.append(item)
             # some races have level-based features (Ex: Aasimar)
             if hasattr(self.race, "features_by_level"):
                 for lvl in range(1, self.level + 1):
-                    fts |= set(self.race.features_by_level[lvl])
+                    for item in list(self.race.features_by_level[lvl]):
+                        fts.append(item)
         if self.background is not None:
-            fts |= set(getattr(self.background, "features", ()))
-
-        return sorted(tuple(fts), key=(lambda x: x.name))
+            for item in getattr(self.background, "features", ()):
+                fts.append(item)
+        return fts
 
     @property
     def custom_features_text(self):