Add a tool to compute how much storage shared images have saved us.

tools/sharedimagestorage.py

@@ -0,0 +1,14 @@
+from data.database import Image, ImageStorage
+
+query = ImageStorage.select().annotate(Image)
+
+saved_bytes = 0
+total_bytes = 0
+
+for storage in query:
+  if storage.image_size is not None:
+    saved_bytes += (storage.count - 1) * storage.image_size
+    total_bytes += storage.count * storage.image_size
+
+print "Saved: %s" % saved_bytes
+print "Total: %s" % total_bytes