Fixed #32 : concept groups are not correctly updated

Fixed #35 : Refactor test helper class (CNC, CC, CIO)
Fixed #36 : Concept values are not used when declared with variable expression
Fixed #37 : Objects in memory lose their values are restart
Fixed #38 : func(a=b, c) (which is not allowed) raise an exception

src/core/utils.py

@@ -444,7 +444,7 @@ def str_concept(t, drop_name=None, prefix="c:"):
     elif prefix == "r:":
         name, id_ = t.metadata.name, t.id
     else:
-        name, id_ = t.key, t.id
+        name, id_ = t.key or t.name, t.id
 
     if name is None and id_ is None:
         return ""