Feedback to user:
  - Status bar: green when recording, moving when loading.
  - Status sounds: when recording starts, when recording ends and when a result (or error) is shown.
  - Error message: shown when there is a recognition error.
  - Audio level bar: depending on the intensity of the voice being recognized.
Smooth Scroll enabled:
  - User can scroll up and down by using the touchpad.
  - When new text is recognized, an automatic scroll-down happens.
Modified OverlayAlertActivity to be independent of the message.