Particles Rewrite

Removal of Current Particle System Code

DNA structures
Main DNA structs may be added back in some way eventually for backward compatibility, but that could also be handled via scripts, since new concepts may not map well onto the old settings.
BKE code
A few of the methods may be re-used later, but better to rewrite the code cleanly then instead of keeping old functions.
RNA
Operators, for Object.particle_systems management and edit mode
UI Python scripts

to do

Add-ons still use particle-related API functions in a number of cases.

	Grep'ing for particle code
	egrep -rni --include=\*.{h,hpp,c,cpp,cc,py,osl,cmake} --include=CMakeLists.txt "psys\|particle\|[^a-zA-Z_]part_\|hair\|strand\|boid\|psmd" .