Added support for log stored in CMS_STORAGE.

Added support for custom value stored in CMS_STORAGE.
Added optional css classes addition to CMS_BLOCK output.
Refactored storage, to manage node from node module code only (or mostly).

TODO: improved view for a cms node, for now hardcoded.

src/kernel/content/format/cms_formats.e

@@ -9,9 +9,8 @@ class
 
 feature -- Access
 
-	item (a_name: detachable READABLE_STRING_GENERAL): CONTENT_FORMAT
+	item (a_name: detachable READABLE_STRING_GENERAL): detachable CONTENT_FORMAT
 		do
-			Result := default_format
 			if a_name /= Void then
 				across
 					all_formats as c