Document social media integration feature

[zopyx]

It is unclear where and how the Twitter/FB account names are exactly used and how social media integration actually works. Adding Twitter and FB does not seem to have any visual impact e.g. on rendering the Plone default front page

[hvelarde]

check the metadata: IIRC, this integration inserts Open Graph and Twitter Cards; see PLIP 20256 for more information

[polyester]

Now documented in the (beta) plone5 docs. http://docs.plone.org/5/en/adapt-and-extend/config/socialmedia.html