Users be able to generated PDF in the DCS repo - unpublished resources

[richmahn]

As a user, I want to be able to download any available PDFs for a repo from the door43.org preview page.

The functionality and UX is as follows:

UX:

• Revert preview page back to show "Conversion in progress" status when HTML not yet generated
• HTML generated on commit and release (tag) from DCS (PDF only on release, see issue #)
• PDF on request (button on preview page Download menu)
  • Fix mouse cursor on Download PDF item (currently a text edit icon)
  • When clicked, Grayed out and unclickable (remove event)
  • Indicate PDF being generated (hourglass next/behind "PDF")
  • Hover-over PDF shows title, PDF being generate
  • Notification box on top of page to report status of all downloadables

Procedure:

• Check if build already in progress for that commit
• On build use build_log.json for HTML status, and build_log_pdf.json for the PDF build status
• If there already is a build_log_pdf.json file when the PDF button is clicked, we immediately serve the PDF or notify the user there were errors
• If no build_log_pdf.json file yet, Javascript in the Door43.org preview page remembers that the user requested a PDF (use cookie?) and to scan to see if a pdf_build_log.json file exists. Once it exists, errors are displayed in red notification box, or link to PDF in green notification box.