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:

• #413 better schema builder - use an external one
• #205 foreign keys - data packages with more than one CSV will typically have foreign key relationships
• #195 Table Schema support

This function should also be supported via the API