Split settings into a quiz card and an application Settings popup

- A Quiz settings button under the player bar opens a small card above
  it with the quiz settings, including Auto repeat, which moves there
  from under the player bar. The card does not dim the quiz, so it can
  be changed during a song, and grows to fit its rows.
- A Settings button in the top bar opens the application settings:
  server, fullscreen and songs to download ahead. Quick sync is gone,
  as the server no longer has it, and the server list is in Settings.
- Labels use sentence case, and seconds to hide show as whole numbers.
- Debug builds switch to the local server and a low winning score in
  the Settings autoload, before any scene asks the server for anything.
  The DEBUG label moves to the top bar, so it shows on every tab.
- Search moves from the top bar back to the quiz toolbar, as the
  Statistics tab has its own search.

tests/integration/test_main_window.gd

@@ -161,15 +161,15 @@ func test_cache_keeps_filling_after_a_failed_download() -> void:
 
 
 func _open_settings() -> void:
-	_press("QuizToolbar/SettingsButton")
+	(_window.get_node("TopBar/SettingsButton") as Button).pressed.emit()
 
 
 func _close_settings() -> void:
-	(_quiz.get_node("SettingsPopup") as Control).visible = false
+	(_window.get_node("SettingsPopup") as Control).visible = false
 
 
 func _press_settings_button(unique_name: String) -> void:
-	(_quiz.get_node("SettingsPopup").get_node("%" + unique_name) as Button).pressed.emit()
+	(_window.get_node("SettingsPopup").get_node("%" + unique_name) as Button).pressed.emit()
 
 
 func test_raising_cache_size_does_not_download_while_settings_are_open() -> void: