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 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.