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

src/core/sheerka/services/SheerkaHistoryManager.py

@@ -35,6 +35,9 @@ class History:
 
         return self.event == other.event and self.result == other.result
 
+    def __hash__(self):
+        return hash((self.event, self.result, self.status))
+
     @property
     def status(self):
         if self._status:
@@ -56,9 +59,6 @@ class SheerkaHistoryManager(BaseService):
     def __init__(self, sheerka):
         super().__init__(sheerka)
 
-    def initialize(self):
-        self.sheerka.bind_service_method(self.history, False)
-
     def history(self, depth=10, start=0):
         """
         Load history