Adds support for currency display (#277)

* Adds a helper function for rendering currency data

* Update helper functions for StockItem model

* Render purchasePrice correctly for stockitem

* Use currency_formatter library instead of money_formatter

* Add total price display for purchase order

* icon fix

lib/l10n/app_en.arb

@@ -1180,6 +1180,9 @@
   "tokenMissingFromResponse": "Access token missing from response",
   "@tokenMissingFromResponse": {},
 
+  "totalPrice": "Total Price",
+  "@totalPrice": {},
+
   "transfer": "Transfer",
   "@transfer": {
     "description": "transfer"