Custom light engine

After a break this MR finally brings the light engine I was waiting for...

(also some bugfixes, changes a lot of other code, breaks a lot of stuff in order to do more rendering async and improve the performance a lot)

Light tasks:

• Fix some bugs (e.g. placing 3 torches and destroying one)
• Decreasing: Ignore direction
• Top and bottom light
• Synchronize light recalculation (clearing light is buggy)
• Benchmark and compare to Startlight
• Recalculate section if edge block light changes: cullface
• recalculate light when solid block changes
• check if light can only go in a direction (otherwise not really realistic, it might can reflect from solid material)
• Light wrong when neighbours are null (edge chunks)
  • or if section is getting created
• check if correct blocks propagate light correctly (aka. is isSolid correct)
• trace block light through null sections
• light is not passing through grass
• check if light can enter block at side (if block is directly next to source)
• mark chunk as updated on skylight change
• Profiling [sometimes placing a block takes 1+ frame to be complete]
• Skylight
  • Heightmap
  • Possibility to mix light
  • Calculate skylight
  • handle heightmap changes
  • handle block changes
  • fluid (water should start flood fill)
  • trace through null sections
• disable light debug mode
• Testing, testing, testing
• [?] light propagation direction (e.g. dirt path)
• check some light todos
• decreasing light algorithm
• check shapes of neighbour (could be done with the culling code, but that even slows down the)
• light when loading chunks (multi threading bug?)
• bare trace (i.e. not creating a section if no blocks are present)
• light not passing through redstone dust, flowers or water
• light filtering blocks (e.g. water, slime block, ...)
• check cobwebs
• light is sometimes not propagating from neighbours correctly (see start from torch)
• border light decreases
• check stairs

Closes #44 (closed)