Creates a particle effect.
- particle: name of the particle definition
- Particle properties can be set here with a preceding '-' or '+'.
- '-' property is set before calling the particle init function
- '+' do it afterwards
- wait: wait time
- Wait times are of the format "a b".
- It spawns particles in random intervals ranging from (a) to (a+b) seconds.
- If no wait time is specified one particle is created at map start.
Don't forget to set the levelflags as needed.