Expanding /ticket return fields

[saupchurch]

Some proposed functions will require the API to provide a richer description of the matrix. The /ticket endpoint seems like the best place to add this. Doing so will convert that endpoint into one that returns a matrix description with the download URL as one of the metadata fields. Other possible fields include: available formats, default units, matrix dimensions and labels for each dimension.

1. Is this something we want to do?
2. Is /tickets the right place for this?
3. What fields should be added?