add runtime field to Simulation

get current scene time

separate simulation eval function

initial testing for integration in depsgraph

Add Boolean Math, Switch and Float Compare function nodes

Since those nodes did not exist for shader node trees before,
I implemented them directly as "function nodes". Those could later
be used in shader node trees as well.

Differential Revision: https://developer.blender.org/D7424

Use some shader nodes in the simulation nodes

This makes a subset of the shader nodes available in simulation node trees.
More can be made available in the future, but we might not be able to actually
implement all the nodes before the release.

For now, their name remains `ShaderNode...`. We should rename them to
e.g. `FunctionNode...` and move them to a separate folder in the future.

Differential Revision: https://developer.blender.org/D7422

Core particle nodes (ui only)

Differential Revision: https://developer.blender.org/D7384

show name in particle simulation node

add missing cases for new types in switch statement

core particle simulation nodes

Merge branch 'image-and-object-socket-type' into influence-and-control-flow-socket-types

Merge branch 'embedded_simulation_node_tree' into image-and-object-socket-type

Merge branch 'simulation-tree-arc' into embedded_simulation_node_tree

Merge branch 'simulation-data-block' into simulation-tree-arc

Merge branch 'master' into simulation-data-block

add missing enum item

add simulation node trees to node tree iterator

fix user counting when freeing interface sockets

copy object/image pointer in node_socket_copy_default_value

bring back a break