Implemented some enhancement request and fixed some bugs

Fixed #2 : Variables are not recognized when inside a rule token
Fixed #15 : Rule: rete attributes are lost when a new ontology is created
Fixed #14 : ReteNetwork: Format rules must not be added to Rete network
Fixed #16 : DefConcept: Variables are not recognized when they are keyword arguments
Fixed #4 : Comparison are not correctly set when comparison property is a concept
Fixed #14 : Parser: merge FunctionParser.NamesNode and ExpressionParser.NamesNode
Fixed #18 : Parser: Add SourceCodeNode test to UnrecognizedNodeParser
Fixed #20 : At startup Number concept is saved in db a numerous number of time
Fixed #21 : CacheManager: I can remove all elements from a ListIfNeededCache and fill it again
Fixed #22 : CacheManager: I can remove all elements from a SetCache and fill it again
Fixed #23 : HistoryManager: history() no longer works
Fixed #24 : HistoryManager: history() no longer works after creating an exec rule
Fixed #25 : SheerkaMemory: Use MemoryObject instead of sheerka.local
Fixed #26 : Debugger: add the list all available services..
Fixed #27 : CONCEPTS_GRAMMARS_ENTRY does not seems to be in use any more
Fixed #28 : Give order to services

tests/non_reg/test_sheerka_non_reg_out.py

@@ -122,3 +122,20 @@ __default__
         assert captured.out == """one: (1001)one
 two: (1002)two
 """
+
+    def test_i_can_retrieve_history(self, capsys):
+        init = [
+            "test()",
+        ]
+        sheerka = self.init_scenario(init)
+        capsys.readouterr()
+
+        sheerka.enable_process_return_values = True
+        res = sheerka.evaluate_user_input(f"history()")
+
+        assert len(res) == 1
+        assert res[0].status
+
+        captured = capsys.readouterr()
+        assert " : test()" in captured.out
+        assert " : history()" in captured.out