API for rectangle & co

Ref #498

docs/general.rst

@@ -265,6 +265,9 @@ The available notification are:
     * link.created
     * link.updated
     * link.deleted
+    * item.created
+    * item.updated
+    * item.deleted
     * log.error
     * log.warning
     * log.info

docs/glossary.rst

@@ -6,6 +6,12 @@ Node
 
 A Virtual Machine (Dynamips, IOU, Qemu, VPCS...), a cloud, a builtin device (switch, hub...)
 
+Item
+-----
+
+Item are visual element not used by the network emulation. Like
+text, images, rectangle... They are pure SVG elements.
+
 Adapter
 -------