I removed bf_blenkernel from `nodes/CMakeLists.txt` again (added it yesterday),
because now this was causing me unresolved symbol errors... Without it, cmake
seems to link the libraries bf_simulation, bf_blenkernel and bf_nodes in the right
order. Not sure if that is just luck or if it is guaranteed.
It was possible to fix the issue by using cmakes `LINK_INTERFACE_MULTIPLICITY`,
but that is probably bad style.
Function names will be updated in a separate commit.
This will be the place for the new particle system and other
code related to the Simulation data block. We don't want
to have all that code in blenkernel.
Approved by brecht.
