Blender Git Loki

Add emitters, events, forces and control flow socket types

This is part of T73324.

The shapes and colors of the sockets will most likely change later on.

This script can be used to create a node with the new socket types:
```
import bpy

class MyCustomNode(bpy.types.Node):
bl_idname = 'CustomNodeType'
bl_label = "Custom Node"

def init(self, context):
self.inputs.new('NodeSocketEmitters', "Emitters")
self.inputs.new('NodeSocketEvents', "Events")
self.inputs.new('NodeSocketForces', "Forces")
self.inputs.new('NodeSocketControlFlow', "Control Flow")

self.outputs.new('NodeSocketEmitters', "Emitters")
self.outputs.new('NodeSocketEvents', "Events")
self.outputs.new('NodeSocketForces', "Forces")
self.outputs.new('NodeSocketControlFlow', "Control Flow")

bpy.utils.register_class(MyCustomNode)

if len(bpy.data.simulations) == 0:
bpy.data.simulations.new("Simulation")

sim = bpy.data.simulations[0]
sim.node_tree.nodes.new("CustomNodeType")
```

Differential Revision: https://developer.blender.org/D7349