About page, text only (not released for translation), first pass.

Design and finalized text to follow. This is just for the RC crowd.

props johnbillion, helen, markjaquith, nacin.
see #30435.

Built from https://develop.svn.wordpress.org/trunk@30821


git-svn-id: http://core.svn.wordpress.org/trunk@30811 1a063a9b-81f0-0310-95a4-ce76da25c4cd