Allow the return of tabular data in addition to JSON

[SimonGoring]

What does this look like for calls to:

• age
• grid
• occ
• pub
• site
• taxon

[SimonGoring]

The plan is to make this work first for JSON. Once this works for JSON, and we've released the API, then we can focus on tabular output.

[jpjenk]

Tabular CSV is available across all primary routes