PostsListFragment Rewrite

This PR is a rewrite of the aged PostsListFragment. It now uses a proper adapter that is backed by an array of 'PostsListsPost' objects for fast loading. Here's a summary of what's new:

 * New design for posts/pages rows. WPTextView was added so the Open Sans font is now used.
 * Used same time 'ago' TextView as in the Reader and Comments views.
 * Post status are displayed in a different color if they are drafts or a locally modified post.
 * Infinite scroll added, no need to tap 'Load more posts' in the footer any longer.

New look:
![screen shot 2014-02-25 at 10 47 39 am](https://f.cloud.github.com/assets/789137/2274347/09fa3144-9f1b-11e3-8cca-7597c97e95b5.png)