title: Is it possible to add a sub route in Python Pyramids Cornice (Rest inspired)
body: <p>I am using Cornice and Pyramids to build an API.
  Most of operation are REST operation so it is very adapted. But for some of them I don't want to follow REST principles.</p>
  
  <p>For exemple in this class using cornice :
  How can we expose an action under : /gianluca/element/{id}/action.</p>
  
  <p>I know I can had another class with path: /gianluca/element/{id}/action with a get or a post function. But I just would like to had this function in a clean way.</p>
  
  <pre><code>from cornice.resource import resource
  from pyramid.security import Allow
  from pyramid.security import Everyone
  
  @resource(collection_path='/gianluca/element', path='/gianluca/element/{id}')
  class MyElement(object):
  
      def __init__(self, request, context=None):
          self.request = request
  
      def __acl__(self):
          return [(Allow, Everyone, 'everything')]
  
      def collection_get(self):
          return {'collection': 'all collection'}
  
      def get(self):
          return "Element id : " + self.request.matchdict['id'] 
  
      # TODO
      def action(self):
          # elementLib.launchElement() 
          # Just a standart web service not in rest but i would like to have it under :
          # /gianluca/element/{id}/action
          return True
  </code></pre>