rethink metadata, make plan

[arlin]

Ideally, the metadata for a tree is downloadable in a form that users can read and process.
Consider the following and come up with a plan for (1) prioritized improvements to the portal, (2) someday-maybe improvements, (3) reply to reviewer:

• the tree metadata in the portal is not downloadable
• the format is plain text with links, no structure
• the content does not include sources and permissions for images

This issue is just to come up with a plan. Then we make a second ticket based on the plan and do that.

[arlin]

The plan is to enable JSON download for the metadata block. The reference list will be handled separately. @ducvan0212, this is what we talked about today. I will open a separate ticket --- see #355