Hide time remaining value in GUI when plugin doesn't auto advance

  - When the playlist doesn't automatically move to the next plugin
     the time remaining doesn't make any sense, so hide that
     bit of information in the case that auto_advance is false
Add Left/Right arrows for navigating plugins in a playlist

  - Replicate UI elements that were already present for navigating
     through available playlists
Initial commit of SoundToLightVisualisationPlugin

  - Sound to light operating in two modes, either EQ or
     scrolling waterfall mode, selectable with A/B on
     the joypad
Add splash screen to SoundToLight Plugin