Configure footnote rendering.

- The config file can provide FootnoteAnchorPrefix, which will be used
  by blackfriday when rendering to HTML. A value of `q:` has the effect
  of making the anchor for a footnote `[^footie]` be `fn:q:footie`. The
  default is `""`.

- The config file can provide FootnoteReturnLinkContents, which will be
  used by blackfriday when rendering to HTML. A value of `^` has the
  effect of making the return link be `^` instead of `[return]`.
Make each generated page’s footnotes unique.

If content pages are fully rendered in a list page, footnotes that use
the same reference (`[^fn]`) will have duplicated anchors. This change
builds on #526 to put the page filename (`Page.File.Name`) as part of
the anchor for a footnote.

This would fix discussion [116](http://discuss.gohugo.io/t/footnote-references-are-duplicated-on-list-pages/116).
Use md5 against the file path for uniqueness.
added In and Intersect template functions
Feed the titleized taxonomy key through string replace to replace '-' with ' ' for proper display of the taxonmy title
#462 fix, remove leading and trailing dashes from urlized slug. includes test changes
Minor fix to error message when copying static files
handle https prefixes in baseUrl