Create packages for bigquery and outline spi layer

[mziccard]

First commit for bigquery module.
Main remarks on BigqueryRpc:

• In bigquery some list endpoints also return the number of total items (list tables and list table data). That might be a useful information to return. Do you think we should return a triple instead of a pair? Our Page interface however does not support such a property.
• list and get methods have explicit names (e.g. listJobs, listTables) as some share the same signature