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/core/test_SheerkaHistoryManager.py

@@ -1,10 +1,11 @@
-from core.sheerka.services.SheerkaHistoryManager import hist
+from core.sheerka.services.SheerkaHistoryManager import hist, SheerkaHistoryManager
 from tests.TestUsingFileBasedSheerka import TestUsingFileBasedSheerka
 
 
 class TestSheerkaHistoryManager(TestUsingFileBasedSheerka):
     def test_i_can_retrieve_history(self):
         sheerka = self.get_sheerka()
+        service = sheerka.services[SheerkaHistoryManager.NAME]
         sheerka.save_execution_context = True
 
         sheerka.evaluate_user_input("def concept one as 1")
@@ -19,7 +20,7 @@ class TestSheerkaHistoryManager(TestUsingFileBasedSheerka):
         sheerka.evaluate_user_input("def concept five as 5")
         sheerka.evaluate_user_input("five")
 
-        h = list(sheerka.history(-1))  # all
+        h = list(service.history(-1))  # all
         assert h == [
             hist("five", True),
             hist("def concept five as 5", True),
@@ -35,13 +36,13 @@ class TestSheerkaHistoryManager(TestUsingFileBasedSheerka):
             hist("Initializing Sheerka.", None)
         ]
 
-        h = list(sheerka.history(2))
+        h = list(service.history(2))
         assert h == [
             hist("five", True),
             hist("def concept five as 5", True)
         ]
 
-        h = list(sheerka.history(2, 2))
+        h = list(service.history(2, 2))
         assert h == [
             hist("four", True),
             hist("def concept four as 4", True),