English doc RSTification part 2: The main directory

One change: the page generated from faq.htm is now located at
faq_historical.rst

Reason being, it appears that most of the faq_ pages and possibly
a couple other pages in maindir/ were the result of faq.htm being
broken apart into separate pieces, because there's a ton of
duplicate content in faq.htm.

I'm not really enthused to do all that work all over again, when
the information is mostly contained in other files. So it'll be
left as-is, waiting to be deleted upstream at a later time. If
there's something to salvage from it, then that can be decided
at that point.