[Kst] healpix status

[Ted Kisner]

The healpix datasource is "working", but still needs some tweaking.  It is 
possible to make plots and use the datasource config widget.  See some 
example plots here:

http://cmb.phys.cwru.edu/kisner/ksthealpix/


Here is a detailed list of features/caveats:

1.  Only cartesian projection until we have a Kst2DRenderer

2.  Radians/degrees units don't work because a negative yStepSize is not 
allowed.  I need to see if this is a matrix, image, or 2dplot limitation.  In 
the mean time, only use RA/DEC or Lat/Lon.

3.  Using readField to read the X/Y head/tail coordinates of the vector field 
is not quite finished- but then we don't have a vectorfield basecurve anyway!  
So this is no big deal...

4.  There are no limits on the projection matrix size, so if you choose one 
too big and use up all your memory, then shame on you ;-)

5.  There is no z-axis colorscale wedge, aside from the token square inside 
the legend.  This is a generally lacking feature which will have to be 
addressed sometime in the future.

Anyway, feel free to test it out- but keep in mind that it's not quite "as 
good as it gets" yet.

cheers,

-Ted