Implement more lights

[Robert42]

• [ ] sunlight
• [ ] tube light
• [ ] disk light
• [ ] rect area light with texture (it already has a t coordinate in range vec2(0)...vec2(1) ) one could use as uv coordinate
  • [x] fix #44 first
  • [x] fix #55 first
  • [ ] why do artefacts appear for a low intensity?
  • [ ] aso check for artefacts, if the rect area light is far away from the wall from the wall or near (event intersecting the wall)