Support upload a Tabular Data Package

[Stephen-Gates]

A Tabular Data Package contains one or more related CSV files and a datapackage.json file that includes the Table Schemas. Enable Octopub to accept data packages that may have been prepared using other tools.

This issue touches on:

• Improve schema builder UX #413 better schema builder - use an external one
• Support foreign keys in datasets #205 foreign keys - data packages with more than one CSV will typically have foreign key relationships
• Form for contributing data based on JSON Table Schema  #195 Table Schema support

This function should also be supported via the API

[Floppy]

This seems like a reasonable thing to do. We'd have to work out how the user workflow happens. The current form is basically a datapackage builder, so should we bypass it completely, autofill it from the datapackage, etc etc?

It might be simplest to add this feature first in the API (to support things like comma chameleon) then add the UI later on.