download method added to image manager

interface/image/ImageManager.py

@@ -5,10 +5,18 @@ class ImageManager:
     def upload_file(self, name, path, format):
         raise NotImplementedError
 
-    def delete(self, id):
+    def get(self, id):
         raise NotImplementedError
 
-    def get(self, id):
+    def download(self, id):
+        raise NotImplementedError
+
+    def download_to_file(self, id, path):
+        f = open(path, 'wb')
+        f.write(self.download(id))
+        f.close()
+
+    def delete(self, id):
         raise NotImplementedError
 
     def list(self):