Show total price of ordered units per article in finance/balancing

* Implement functions total_price and total_gross_price on model
order_article
* Show total_price and total_gross_price in view finance/balancing
 _order_article (Closed #108)

app/models/order_article.rb

@@ -77,6 +77,16 @@ class OrderArticle < ActiveRecord::Base
     units += ((remainder > 0) && (remainder + tolerance >= unit_size) ? 1 : 0)
   end
 
+  # Calculate price for ordered quantity.
+  def total_price
+    units_to_order * price.price
+  end
+
+  # Calculate gross price for ordered qunatity.
+  def total_gross_price
+    units_to_order * price.gross_price
+  end
+
   def ordered_quantities_equal_to_group_orders?
     (units_to_order * price.unit_quantity) == group_orders_sum[:quantity]
   end

app/views/finance/balancing/_order_article.html.haml

@@ -8,8 +8,14 @@
   - unless order_article.ordered_quantities_equal_to_group_orders?
     %span{:style => "color:red;font-weight: bold"} !
 %td= order_article.price.unit_quantity.to_s + ' * ' + order_article.article.unit.to_s
-%td= number_to_currency(order_article.price.price, :unit => "")
+%td
-%td= number_to_currency(order_article.price.gross_price, :unit => "")
+  = number_to_currency(order_article.price.price, :unit => ""), |
+  "/ ", |
+  number_to_currency(order_article.total_price, :unit => "") |
+%td
+  = number_to_currency(order_article.price.gross_price, :unit => ""), |
+  "/ ", |
+  number_to_currency(order_article.total_gross_price, :unit => "") |
 %td= order_article.price.tax
 %td= order_article.price.deposit
 %td