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/TestUsingMemoryBasedSheerka.py

@@ -15,6 +15,10 @@ class TestUsingMemoryBasedSheerka(BaseTest):
             while TestUsingMemoryBasedSheerka.sheerka.om.current_ontology().name != self.root_ontology_name:
                 TestUsingMemoryBasedSheerka.sheerka.pop_ontology(self.context)
 
+            for service_name, service in TestUsingMemoryBasedSheerka.sheerka.services.items():
+                if hasattr(service, "reset_state"):
+                    service.reset_state()
+
     @staticmethod
     def new_sheerka_instance(cache_only):
         sheerka = Sheerka(cache_only=cache_only)