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/management/base_controller.rb

@@ -1,6 +1,7 @@
 class Management::BaseController < ActionController::Base
   include GlobalizeFallbacks
   layout "management"
+  default_form_builder ConsulFormBuilder
 
   before_action :verify_manager
   before_action :set_locale