plugin XEP-0054, quick frontend(app): various improvments:

- memory.cache is now used
    - getAvatar and setAvatar has been renamed to avatarGet and avatarSet to follow new convention
    - getAvatar now return (optionally) full path, and may request vCard or only return avatar in cache
    - getAvatarFile has been removed as it is not needed anymore (avatarGet can return full path)
    - getCard has been removed from bridge as it was only used to request avatar
    - new internal method getBareOfFull return jid to use depending of the jid being part of a MUC or not
    - cache is now set per profile in client, instead of a general one for all profiles
    - thanks to the use of memory.cache, correct extension is now used in saved file, according to MIME type
    - fixed and better cache handling
    - a warning message is shown if given avatar hash differs from computed one
    - empty hash value is now in a constant, and ignored if received
    - QuickApp has been updated to follow new behaviour
    - Primitivus has been fixed (it was not declaring not using avatars correclty)
    - jp has been updated to follow new methods name

frontends/src/primitivus/primitivus

@@ -280,7 +280,7 @@ class PrimitivusTopWidget(sat_widgets.FocusPile):
 
 class PrimitivusApp(QuickApp, InputHistory):
     MB_HANDLER = False
-    AVATAR_HANDLER = False
+    AVATARS_HANDLER = False
 
     def __init__(self):
         bridge_module = dynamic_import.bridge(bridge_name, 'sat_frontends.bridge')