Adds new high-res night sky.
Merge pull request #441 from skaldarnar/develop

Some minor tweaks to block placement handling and some blocks.
Adds some minor tweaks.

- Adds a new property that can be used to set the blur intensity on the sky (current defaults to 100%)
- Fixes that motion blur with a blur intensity of 0 was active but almost invisible
- Adds various other properties to the Post Processing Renderer
- Adds new enum for various FBO types (more to come) to the Post Processing Renderer
Halves the amount of samples used for the light shafts post processing effect.
Adjusts luminance.
Added some extra checks into StringMapType serialization, so that null values are not serialized.
Fixed BlockChangedEvents not being sent when the player places a block.
Increased initial distance for dropped blocks and made inventories persistent for dropped blocks.
* increased distance to 2, blocks thrown away while looking down are no longer picked up directly
* removed deprecated method use
* store placedEntity for dropped blocks

Fixes #310