Fix for issue #155

I made the changes to add start/end/up/down to the list of action values. I also updated left and right to refer to logical positioning. This was to fix I18N issue #155 Bidi Considerations (https://github.com/w3c/personalization-semantics/issues/155 <https://github.com/w3c/personalization-semantics/issues/155>)

You can view the draft here:  https://raw.githack.com/w3c/personalization-semantics/issue155/content/index.html#values <https://raw.githack.com/w3c/personalization-semantics/issue155/content/index.html#values>

Becky Gibson
Sr. Accessibility Strategist
Knowbility.org

The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI)
Co-Chair, Accessible Platform Architectures	http://www.w3.org/wai/apa