Support the "enter" key from a physical keyboard (#379)

* Support the "enter" key from a physical keyboard

I often have a usb keyboard dangling from my printer, and got annoyed I couldn't just hit enter from the console.

https://docs.gtk.org/gtk3/signal.Entry.activate.html

* Fix whitespace for linting

panels/console.py

@@ -51,6 +51,7 @@ class ConsolePanel(ScreenPanel):
         entry.set_hexpand(True)
         entry.set_vexpand(False)
         entry.connect("focus-in-event", self._show_keyboard)
+        entry.connect("activate", self._send_command)
 
         enter = self._gtk.Button("Send")
         enter.set_hexpand(False)