Show purchase weight on admin details page

This PR goes with PR #861 

Shows purchase weight on admin details page if purchase weight is non-zero   This makes all information required to create a shipping label available in one place.

Fixed section titles to not have duplicates.

Changed header elements to consistently use blockquotes rather than paragraphs.

Added style information that tightens up the page a little bit show more information.  It might have changed a little bit with the revised WordPress admin UI. Most of the space was gained with the change to the top margin on the table data elements for the totals.  Screen shot of adjusted items details screen follows.

![item-details](https://f.cloud.github.com/assets/3098792/2015131/a90fa758-87b2-11e3-92cd-ddaec16c6705.png)