Blender Git Loki

Geometry Nodes: Poisson disk point distribution node/method

This patch does two things:
* Introduce a Seed to the random distribution method
* Bring in a new distribution method for the point scattering node

Patch Review: https://developer.blender.org/D9787

Note: This commit doesn't not handle doversion. Which means that users
need to manually update their files that were using the Point Distribute
node and reconnect inputs to the "Maximum Density" socket.

Original patch by Sebastian Parborg, with changes to not rely on the cy
libraries and overall cleanup.

Patch review by Jacques Lucke, besides help with the new "heap" system
that was required for this algorithm.

Based on Cem Yuksel. 2015. Sample Elimination for Generating Poisson Disk
Sample. Sets. Computer Graphics Forum 34, 2 (May 2015), 25-32
http://www.cemyuksel.com/research/sampleelimination/