[Tails-dev] reworking About, Overview and Features

Hi,

Still working on the doc-rework branch. I'm unhappy with the current
pages about.html, doc/overview.mdwn and features.mdwn. They are often
redundant, not as concise as they could be, etc.

I think I will :
- merge the About and Overview pages
- move the licensing into a separate page
- remove the introduction of the Features page
- link the Features page at the end of the Overview

Any more suggestion?

--
sajolida