Map metadata correctly for supported IFDO vocab

[habaldwin01]

Enable export of project metadata as iFDO file. Use functionality as a way to snapshot a project.

[habaldwin01]

Basic functionality implemented in f5638ea, although needs to be fleshed out with better metadata support

[habaldwin01]

Considered a backwards-compatibility mode for old workflows - ideally this feature will be deprecated with adoption of schema-based vocab on the croissant export.