Add correct grants to role so they can execute functions and use data

[ortonomy]

In the last part of the postgraphql tutorial it adds table and row level security to tables.

The schema needs completing using the tutorial as a guide. https://github.com/postgraphql/postgraphql/blob/master/examples/forum/TUTORIAL.md

This'll have a dependency on finishing all the functions, and triggers for V1.

[ortonomy]

Done!