core, plugin XEP-0115: discovery refactoring:

- hashing algorithm of XEP-0115 has been including in core
    - our own hash is still calculated by XEP-0115 and can be regenerated with XEP_0115.recalculateHash
    - old discovery methods have been removed. Now the following methods are used:
        - hasFeature: tell if a feature is available for an entity
        - getDiscoInfos: self explaining
        - getDiscoItems: self explaining
        - findServiceEntities: return all available items of an entity which given (category, type)
        - findFeaturesSet: search for a set of features in entity + entity's items
      all these methods are asynchronous, and manage cache automatically
    - XEP-0115 manage in a better way hashes, and now use a trigger for presence instead of monkey patch
    - new FeatureNotFound exception, when we want to do something which is not available
    - refactored client initialisation sequence, removed client.initialized Deferred
    - added constant APP_URL
    - test_plugin_xep_0033.py has been temporarly deactivated, the time to adapt it
    - lot of cleaning

src/plugins/plugin_xep_0050.py

@@ -205,7 +205,7 @@ class XEP_0050(object):
                                  'FORBIDDEN', 'ITEM_NOT_FOUND', 'FEATURE_NOT_IMPLEMENTED', 'INTERNAL'))(('bad-request', 'malformed-action'),
                                  ('bad-request', 'bad-action'), ('bad-request', 'bad-locale'), ('bad-request','bad-payload'),
                                  ('bad-request','bad-sessionid'), ('not-allowed','session-expired'), ('forbidden', None),
-                                 ('item-not-found', None), ('feature-not-implemented', None), ('internal-server-error', None)) # XEP-0050 §4.6 Table 5
+                                 ('item-not-found', None), ('feature-not-implemented', None), ('internal-server-error', None)) # XEP-0050 §4.4 Table 5
 
     def __init__(self, host):
         info(_("plugin XEP-0050 initialization"))