Add CreateImage that creates a new image from a running server
diff --git a/interfaces.go b/interfaces.go
index 725b602..8d5887c 100644
--- a/interfaces.go
+++ b/interfaces.go
@@ -128,6 +128,9 @@
 	// Other providers may reserve the right to act on additional fields.
 	RebuildServer(id string, ns NewServer) (*Server, error)
 
+	// CreateImage will create a new image from the specified server id returning the id of the new image.
+	CreateImage(id string, ci CreateImage) (string, error)
+
 	// Addresses
 
 	// ListAddresses yields the list of available addresses for the server.