Import doco from docs@friendicared.net

Changed the default help page to load main.bb so we can let folk edit the webpage instead of being put off by big bad scary git, and imported the first batch of doco.  There's a bit of new stuff, but it's mostly a case of getting it in sync with what's already there.  The markdown has not been removed in case we missed anything.  We clear that out over the coming days.