plugins improvement

- new protocols field in plugins info, useful to know which ones are implemented by the plugin
- XEP-0153 first implementation (vcard avatars)
- plugin vcard: avatar & nick cached, clients are noticed of updated values

plugins/plugin_xep_0065.py

@@ -83,6 +83,7 @@ PLUGIN_INFO = {
 "name": "XEP 0065 Plugin",
 "import_name": "XEP_0065",
 "type": "XEP",
+"protocols": ["XEP-0065"],
 "main": "XEP_0065",
 "description": """Implementation of SOCKS5 Bytestreams"""
 }