Extracted page support from cms_node_module, and add a proper CMS_PAGE_MODULE.

- now, the CMS_PAGE_MODULE has to be declared in the related CMS_SETUP via CMS_EXECUTION.
   (See demo for example)

Improved the export facilities.
  Implemented blog and page export.
Added import facilities.
  Implemented blog and page import.

Improved node revision web interface (allow to edit a past revision, in order to restore it as latest revisionm i.e current).
Removed specific tag from blog module, and reuse the taxonomy module for that purpose.

Added WIKITEXT module that provide a WIKITEXT_FILTER, so now we can have wikitext content.
   - for now, no support for wiki links such as [[Foobar]].

modules/node/persistence/cms_node_storage_i.e

@@ -140,19 +140,22 @@ feature -- Access
 			expected_type: across Result as ic all ic.item.content_type.same_string (a_node_type.name) end
 		end
 
-feature -- Access: outline
-
-	children (a_node: CMS_NODE): detachable LIST [CMS_NODE]
-			-- Children of node `a_node'.
-			-- note: this is the partial version of the nodes.
-		deferred
-		end
-
-	available_parents_for_node (a_node: CMS_NODE): LIST [CMS_NODE]
-			-- Given the node `a_node', return the list of possible parent nodes id
-		deferred
-		ensure
-			a_node_excluded: across Result as ic all not a_node.same_node (ic.item) end
+	nodes_of_type_with_title (a_node_type: CMS_CONTENT_TYPE; a_title: READABLE_STRING_GENERAL): LIST [CMS_NODE]
+			-- List of nodes of type `a_node_type' with title `a_title`.
+			--| Redefine to optimize!	
+		do
+			Result := nodes_of_type (a_node_type)
+			from
+				Result.start
+			until
+				Result.after
+			loop
+				if a_title.same_string (Result.item.title) then
+					Result.forth
+				else
+					Result.remove
+				end
+			end
 		end
 
 feature -- Change: Node