Attractor field mk2

Слиты nikitronn запросил слияние attractor_field_mk2 в master

Created by: portnov

This adds:

  • Mesh Edges mode: attract to the edges of the mesh. This is the cause of Mk2 - I had to add a new input.
  • Circle mode: attract to the circle defined by center, radius and normal vector.
  • All modes (except for "Mesh Faces") can now work with multiple attractors at once; fields generated by different attractors can be merged by "Average" or "Nearest" operation.

Screenshot_20200517_173357 Screenshot_20200517_204452 Screenshot_20200517_204606 Screenshot_20200517_220941 Screenshot_20200517_221516 Screenshot_20200517_223653 Screenshot_20200517_223835 Screenshot_20200517_224124

Preflight checklist

Put an x letter in each brackets when you're done this item:

  • Code changes complete.
  • Code documentation complete.
  • Documentation for users complete (or not required, if user never sees these changes).
  • Manual testing done.
  • Unit-tests implemented.
  • Ready for merge.