Added the `:orphan:` file-wide metadata field

The <a href="http://sphinx-doc.org/markup/misc.html#file-wide-metadata"><code>:orphan:</code></a> field suppresses the Sphinx error that occurs when a file in the source directory doesn't appear in a `toctree` directive.
Removed `foreword.rst` from hidden `toctree`

The `foreword.rst` file was used in printed versions, but currently it is not being used, so it shouldn't appear in any `toctree` directives.
use :orphan: for latexindex too