Added `StopCommand` and `RestartCommand`.

platypush/commands/_commands/__init__.py

@@ -0,0 +1,2 @@
+# flake8: noqa
+from ._app_ctrl import *

platypush/commands/_commands/_app_ctrl.py

@@ -0,0 +1,25 @@
+from typing_extensions import override
+
+from platypush.commands import Command
+
+
+class StopCommand(Command):
+    """
+    Stop the application.
+    """
+
+    @override
+    def __call__(self, app, *_, **__):
+        self.logger.info('Received StopApplication command.')
+        app.stop()
+
+
+class RestartCommand(Command):
+    """
+    Restart the application.
+    """
+
+    @override
+    def __call__(self, app, *_, **__):
+        self.logger.info('Received RestartApplication command.')
+        app.restart()