added format_currency and added options to all currency fields

accounts/doctype/account/account.txt

@@ -2,7 +2,7 @@
  {
   "creation": "2013-01-19 10:23:33", 
   "docstatus": 0, 
-  "modified": "2013-01-22 15:05:18", 
+  "modified": "2013-01-23 17:11:26", 
   "modified_by": "Administrator", 
   "owner": "Administrator"
  }, 
@@ -169,7 +169,7 @@
   "description": "Rate at which this tax is applied", 
   "doctype": "DocField", 
   "fieldname": "tax_rate", 
-  "fieldtype": "Currency", 
+  "fieldtype": "Float", 
   "hidden": 0, 
   "label": "Rate", 
   "oldfieldname": "tax_rate", 
@@ -207,6 +207,7 @@
   "label": "Credit Limit", 
   "oldfieldname": "credit_limit", 
   "oldfieldtype": "Currency", 
+  "options": "eval:erpnext.get_currency()", 
   "permlevel": 0, 
   "print_hide": 1
  },