Initial import of the Twenty Twelve theme, by Drew Strojny. This time around...

Initial import of the Twenty Twelve theme, by Drew Strojny. This time around we're trying something different than the previous twenty-something themes, a much more minimalist approach that affords easy use as a CMS in addition to being blog-forward. More information will be on wpdevel soon. Props drewstrojny and lancewillett.

git-svn-id: https://core.svn.wordpress.org/trunk@19842 1a063a9b-81f0-0310-95a4-ce76da25c4cd