Added physical/comoving coordinate info to image plots.
	modified:   plotting.py
Turn off axes.
	modified:   plotting.py
Separate structure visualization scripts superseded by structure.py
	deleted:    structure_box.py
	deleted:    structure_disk.py
	deleted:    structure_halo.py
Removed deprecated.
	deleted:    scripts/halo3D.py
	deleted:    scripts/morphology.py
	deleted:    scripts/particles3D.py
	deleted:    scripts/tvr.py
Keep t_form annotation on image.
	modified:   plotting.py
Make use of multiprocessing in multitask() optional.
	modified:   pyGadget/sim.py
	modified:   scripts/structure.py
Fixed sink loading bugs.
	modified:   sim.py
	modified:   sink.py
Asciitable package is deprecated.  Porting to astropy.io.ascii
	modified:   sink.py
electron frac is a derived quantity -- don't refine again.
	modified:   sph.py
Convert axes plotting functions to staticmethods.
	modified:   plotting.py
Added CMB floor to gas temp phase plots.
	modified:   plotting.py
Adjusted HDfrac plot limits.
	modified:   plotting.py
Make colorbar on images optional.
	modified:   plotting.py