Added options to set page size, orientation, and unit of measurement. Text in admin UI now reflects units of measurement now in use (default is mm, and all values are in mm). Worked around difficulty rendering SVG images by removing them and rendering placeholder text (the link is still active). More work done on trying to preserve image alignment.

git-svn-id: https://plugins.svn.wordpress.org/wp-post-to-pdf-enhanced/trunk@872515 b8457f37-d9ea-0310-8a92-e5e31aec5664