UI: Add a "New" button for the particle system, consistent to other areas like materials, world and textures.

Differential Revision: https://developer.blender.org/D171

release/scripts/startup/bl_ui/properties_particle.py

@@ -107,6 +107,8 @@ class PARTICLE_PT_context_particles(ParticleButtonsPanel, Panel):
         if psys is None:
             part = particle_get_settings(context)
 
+            layout.operator("object.particle_system_add", icon='ZOOMIN', text="New")
+
             if part is None:
                 return