Pod fixes

Hello,

This branch fixes a bunch of errors in the documentation.  The first fixes some out-of-order methods that appear before NAME in Worksheet.pm and Workbook.pm.  The second patches fixes a pod error and an actual documentation error (an incorrectly named method). The third is just a simple pod formatting fixes.  The fourth adds links back to the main document (Spreadsheet::ParseExcel) in the modules without any significant documentation.  Please let me know if you'd like me to make any changes.  Thanks for your time and effort and have a great day!

Cheers,
Fitz