WebGLApplication: add option to smooth skeletons with a Gaussian convolution.
WebGLApplication: add option to smooth skeletons with a Gaussian convolution.

It is surprisingly fast and looks great, removing all jitter.

Could be made even faster by caching distance measurements.

fzadow/CATMAID,fzadow/CATMAID,htem/CATMAID,fzadow/CATMAID,htem/CATMAID,htem/CATMAID,htem/CATMAID,fzadow/CATMAID