Further pdf improvements

Closes #288 (closed)

• Better defaults for what pages are exported
  • Remove license text from PDF
  • No longer include all pages for BOM items in PDF. Remove these links automatically in PDF output, preserving any overriding of the text with preceeding text in []s
• Add configuration option to add extra pages to the pdf
• stop includetext feature crashing if a newline is within the quoted text
• stop errant warning that title image was doubly defined
• Reformat and forward weasyprint warnings as GitBuilding warnings.
• Split out website and pdf specific CSS
• Improve PDF formatting