Refactor to use JSON to transmit collection and image data
Remove implict bullet behavior

Carriage returns are not consistently converted into bullets
by MS-Office vs. LibreOffice vs. OpenOffice vs. Keynote.
So I've removed the implicit (carriage return) bullets, added
explict bullets for the title page, and added metadata headings
for individual slide metadata.
Merge pull request #211 from curationexperts/powerpoint_export

Powerpoint export updates