"Export" additions

[cgmeyer]

It would be nice to be able to do the following (use case in parentheses):

1. Export an archive containing TSVs of all nodes in an entire project (for easy editing/analysis/sharing of a single project)
2. Export an archive containing TSVs of all nodes in every project of the entire commons that a user has access to, that is, export all data in the commons (for backup of the commons prior to a major change)
3. Export a particular node for all projects (for backing up the data in a particular node across the commons in the case of a major change to a single node, like changing links, name of the node, or required properties).