Return Quantity progenies as a result of partial ordering

Separate scope only provided some optimisation by reducing the count of
records :numbered and should be unnecessary in future once numbering
can be merged with ordering into one recursive query

app/controllers/quantities_controller.rb

@@ -48,7 +48,7 @@ class QuantitiesController < ApplicationController
 
     @ancestors = @quantity.ancestors
     @quantity.depth = @ancestors.length
-    @self_and_progenies = @quantity.progenies.unshift(@quantity)
+    @self_and_progenies = @quantity.with_progenies
     @before = @self_and_progenies.last.successive
   end