slightly more consistent capitalisation of ikiwiki

slightly more consistent capitalisation of ikiwiki

For a while, I was avoiding capitalizing ikiwiki at the beginning of a
sentence. I now think that's a bad idea (unless explicitly referring to
the `ikiwiki` command). Still, I don't go all the way and always cap it,
as a proper noun. That would make the logo look bad. ;)

I also tend to avoid capping it as IkiWiki, except when referring to the
perl internals, which do use that capitalization. (Too late to change
that.) However, it's also reasonable to do so in a WikiLink, as a nod to
historical camelcase wikis.