add gaseous-giganticus
gaseous-giganticus: add simplex noise code from Stefan Gustavson

Originally GPL licensed but later donated to public domain

Obtained code from here:
https://github.com/kev009/craftd/tree/master/plugins/survival/mapgen/noise

Signed-off-by: Stephen M. Cameron <stephenmcameron@gmail.com>
Add simplex noise to makefile
progress on gaseous-giganticus
more progress on gaseous-giganticus
gaseous-giganticus: initialize particle colors from image
gaseous-giganticus: make output images
gaseous-giganticus: work on unrotation of rotated and projected noise gradient vector
gaseous-giganticus: Use a better way of projecting noise gradient vector into sphere surface
gaseous-giganticus: curl different ways depending if gradient is up- or down-hill.

This is definitely necessary to get rotation about hills and depressions in noise gradient field.
gaseous-giganticus: adjust particle count
gaseous-giganticus: adjust noise scale
gaseous-giganticus: misc debug of png scaling (programming is hard).

This is all related to png scaling.  I do not understand how pngs work.
gaseous-giganticus: blend pixels over time
gaseous-giganticus: add octaves of noise (4).
gaseous-giganticus: more debug trying to get rid of velocity divergence
gaseous-giganticus: fade out background
gaseous-giganticus: more trying to get rid of velocity divergences

I think it has to do with how we decided whether or not a noise gradient is
uphill or downhill.  Put in a 0.95 fudge factor, which improved things a lot,
but do not know how to figure the "right" answer (or even if there *is* a right
answer that avoids divergences.
gaseous-giganticus: Fix style of simplex noise code