Links to all gEDA project member sites on the main page

I think the geda-project.org should have links to all the gEDA
member projects regardless of a logo existence for them. If a
project has no logo, there should be a text link to its site.

I consider the main project page should provide the easy way to
find any gEDA associated project. There are plenty of them and
even after a long time working with gEDA and its site I cannot
sometimes easily find some of the projects.

So I suggest to add:
  * ngspice (http://ngspice.sourceforge.net/)
  * gnucap (gnucap.org or http://gnucap.org/dokuwiki/doku.php?id=gnucap:start)
  * spicelib/gedaparts (http://www.h-renrew.de/h/spicelib/doc/index.html)
  * gspiceui (http://sourceforge.net/projects/gspiceui/)
  * xgsch2pcb (is there a dedicated page for it?)
  * gparts (http://wiki.geda-project.org/geda:gparts_tc ?)