Blender Git Loki

Cycles: Add control for sun intensity in Sky Texture and change altitude to km

Differential Revision: https://developer.blender.org/D8091

Cycles: Add versioning code for the new Sky Texture model

Differential Revision: https://developer.blender.org/D8091

Cycles: Remove Vector input on Sky texture when using the included sun

When using the sun, we need to sun sampling logic to avoid excessive
sampling map resolution, but that logic assumes that the Vector input
comes from the view direction.
That is the case in the vast majority of cases anyways, so the easiest
solution is to just remove the input for that case.

Differential Revision: https://developer.blender.org/D8091

Cycles: Remove limits on the Sky texture's sun rotation

For animation/driver purposes, being able to go outside of the 0-360
range makes things easier.

Differential Revision: https://developer.blender.org/D8091

Cleanup: unused debug variable

Particles: initial support for forces in simulation node trees

The force node can now be used to control the behavior of particles.
Forces can access particles attributes. Currently, there are three attributes:
`Position` (vector), `Velocity` (vector) and `ID` (integer).

Supported nodes are: Math, Vector Math, Separate Vector, Combine Vector and Value.

Next, I'll have to split `simulation.cc` into multiple files and move
some stuff out of blenkernel into another folder.

Nodes: support more implicit conversions in simulation node tree

Functions: minor improvements

Cleanup: disable debug code

Functions: minor api improvements

GPencil: Replace "ShaderFX" with "Shader Effects" in RNA prop text

Nodes: support implicit conversions and incorrectly linked sockets

Fix: incorrect attribute type in network

Nodes: support vector math node in simulation node tree

Nodes: support math node in simulation node tree

Nodes: support Value node in simulation node tree

Nodes: move Math, Vector Math and Value shader nodes to c++ files

This required a little bit of refactoring, because we were using c-only
syntax for the gpu shader names. All tests are still passing.

UV: add path select operator that uses the selection

Instead of using the mouse cursor position,
this selects between existing selected elements.

Access this since picking a selection path doesn't
work from the menu.

Cleanup: remove unused function

Cleanup: spelling