Update hard-coded currency UI with currency specific params (#488)

* Update hard-coded currency UI with currency specific params

* Rename extension methods to match currency option names; Move cents extension to numeric class extension

* Use currency's precision to show the cents part in accounts show page

---------

Co-authored-by: Sriram Krishnan <sriram@seafoodsouq.com>

config/initializers/string_extensions.rb

@@ -0,0 +1,13 @@
+class String
+  def unit
+    CURRENCY_OPTIONS[self.to_sym][:unit]
+  end
+
+  def separator
+    CURRENCY_OPTIONS[self.to_sym][:separator]
+  end
+
+  def precision
+    CURRENCY_OPTIONS[self.to_sym][:precision]
+  end
+end