As a developer, I want to contribute to this project

[bruchansky]

Refactor needed before the code is ready for contributions:

• make ArtScene a subclass of Scene
• create a class per type of viewpoints:
  -- simple: a simple dot with a viewpoint
  -- teleportation: teleports you to far away or otherwise unreachable viewpoint
  -- text plynth: viewpoint with a text
  -- image plynth: viewpoint with an image + text
  -- carousel plynth: viewpoint with rotating text
  -- audio plynth: viewpoint with an audio + text
  -- exhibit plynth: viewpoint with a mesh + text + optional audio
• refactor coordinates so that they always follow conventions
• refactor navigation mechanics

[bruchansky]

486a827