Put icons for popgen, statgen, phylogeny at top

[hyanwong]

I think the "genetics research" page (which may be one of the first that people go to after the front page) suffers a little from having the links to popgen, statgen, etc buried in the text. Could we pull these out into the top by using the nice icons that have been made, e.g. roughly like

[benjeffery]

Thanks, @hyanwong.
I agree that the categories are a little non-obvious. I'll do a website pass in a month or so, and have added this to a milestone for then.