Create a "version 2" of the `.pnd` format

[vdye]

Add versioning to the .pnd XML format, and include a number of fixes:

• Fix 0.6ft y-axis error (see Improve the PDF drill rendering #41) in the rank positioning code, so all .pnd files going forward have the fix.
• Position ranks based off of the front sideline instead of the back.
• Add a "version" field to the XML to track this, with "unversioned" being treated as v1

Additionally, include backward compatibility handling to adjust the rank positions automatically before saving in the v2 format.