Matched Python APIs. (#319)

Author: ATATC

src/Controller.h

@@ -18,7 +18,7 @@ class Controller : public Device<T> {
 public:
     Controller() : Device<T>() {}
     int level() { return this->_parentTags.size(); }
-    ArrayList<Device<E>> devices() { return _devices; }
+    const ArrayList<Device<E>> &devices() { return _devices; }
     void device(const String &tag, Device<E> device) { _attachDevice(tag, device); }
     Device<E> device(const String &tag) { return _devices.get(_device_tags.indexOf(tag)); }
     virtual void initialize(const ArrayList<String> &parentTags) {