Change stack viewer for main site

[Marta Costa]

Currently in R/zzz.R

vfbr.server="http://vfbdev.inf.ed.ac.uk",

could this be to main site

http://www.virtualflybrain.org

And in R/vfb_nblast.R

server="http://vfbdev.inf.ed.ac.uk"

[Gregory Jefferis]

See #8