doc pages need links

[alanedelman]

both forwards and backwards to the next/previous sections

[StefanKarpinski]

Yeah, it's pretty annoying that the wiki format doesn't provide this, so I guess we need to add them by hand. Oh well.

[ViralBShah]

Probably some shell scripting magic. Would be cool if one can do this with julia. We probably have all the string processing and unix integration to consume the wiki pages automatically, and insert links.

[StefanKarpinski]

I added a ./fixup script in the julia.wiki repo that takes no args and replaces (or adds) a footer section to each page linked to from Home. To update (regenerate) the footer sections on each page, just rerun this script and commit the updated pages in the wiki repo.