Turn bess into an engine so we can share generators

gems/bess/lib/houdini.rb

@@ -2,7 +2,7 @@
 
 # License: AGPL-3.0-or-later WITH WTO-AP-3.0-or-later
 # Full license explanation at https://github.com/houdiniproject/houdini/blob/master/LICENSE
-require "houdini/railtie"
+require "houdini/engine"
 
 module Houdini
   extend ActiveSupport::Autoload

gems/bess/lib/houdini/engine.rb

@@ -3,7 +3,7 @@
 # License: AGPL-3.0-or-later WITH WTO-AP-3.0-or-later
 # Full license explanation at https://github.com/houdiniproject/houdini/blob/master/LICENSE
 module Houdini
-  class Railtie < ::Rails::Railtie
+  class Engine < ::Rails::Engine
     config.houdini = ActiveSupport::OrderedOptions.new
 
     config.houdini.core_classes = {supporter: 'Supporter', nonprofit: 'Nonprofit'}