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/parsers/BaseNodeParser.py

@@ -231,8 +231,7 @@ class ConceptNode(LexerNode):
 
     def clone(self):
         # do we need to clone the concept as well ?
-        clone = ConceptNode(self.concept, self.start, self.end, self.tokens, self.source, self.underlying)
-        return clone
+        return ConceptNode(self.concept, self.start, self.end, self.tokens, self.source, self.underlying)
 
     def as_bag(self):
         """
@@ -305,6 +304,16 @@ class SourceCodeNode(LexerNode):
     def get_source_to_parse(self):
         return self.python_node.source
 
+    def clone(self):
+        clone = SourceCodeNode(
+            self.start,
+            self.end,
+            self.tokens,
+            self.source,
+            self.python_node,
+            self.return_value)
+        return clone
+
 
 class SourceCodeWithConceptNode(LexerNode):
     """
@@ -413,6 +422,8 @@ class SourceCodeWithConceptNode(LexerNode):
 
     def clone(self):
         clone = SourceCodeWithConceptNode(self.first, self.last, self.nodes.copy(), self.has_unrecognized)
+        clone.python_node = self.python_node
+        clone.return_value = self.return_value
         return clone
 
     def to_short_str(self):