Fixed default for singletracks: xrange(10000)

also, S**2 --> A

	modified:   otracks.py
	modified:   tracks.py
Better plotting options for several codes

fps and particle size give proper units

cosmetics

	modified:   msds_v_density.py
	modified:   orientation.py
	modified:   otracks.py
	modified:   tracks.py
Typo! fix spelling of psim -> psims to match def

	modified:   correlation.py