Updated code development to separate functionality into separate files.
  Main file: SceneNavigator.pde
  Sub files: SN_KeyboardInput.pde - UI Keyboard support
             SN_MouseInput.pde    - UI Mouse Support

Added basic keyboard UI functions:
  'w'    - Move viewing frustrum forward
  's'    - Move viewing frustrum backwards
  'a'    - Rotate viewing frustrum left
  'd'    - Rotate viewing frustrum right
  'v'    - Toggle viewing offset. (relative offset instead of being fixed)
  'D'    - Toggle scene display.
   UP    - pan viewing frustrum up.
   DOWN  - Pan viewing fristrum down.
   RIGHT - Pan viewing frustrum right.
   LEFT  - Pan viewing frustrum left.

Added start of mouse UI functions:
   Turn off mouse pointer.
   Added mouse tracking in viewpoint UV coordinates.