Inherit from builder instead of monkey patching it

We were monkey-patching FoundationRailsHelper::Formbuilder, which made
form customization difficult. We can inherit from it, which is the
standard way of extending what an existing class does, and make our form
the default one.

app/controllers/application_controller.rb

@@ -6,6 +6,7 @@ class ApplicationController < ActionController::Base
   include HasOrders
   include AccessDeniedHandler
 
+  default_form_builder ConsulFormBuilder
   protect_from_forgery with: :exception
 
   before_action :authenticate_http_basic, if: :http_basic_auth_site?