Help: Show abilities and ability upgrades separately

Fixes #2907

(cherry picked from commit 9e7988a)

src/units/types.cpp

@@ -287,7 +287,7 @@ void unit_type::build_help_index(
 			}
 
 			for(const config::any_child& ab : abil_cfg.all_children_range()) {
-				abilities_.emplace_back(ab.cfg);
+				adv_abilities_.emplace_back(ab.cfg);
 			}
 		}
 	}