Queries for all elements

[schroeer]

Again referring to the example setup of #15.

Another thing that I would like to have is queries such as allPeople. They could easily be made from the existing plural queries by making the id non-mandatory:

type Query {
  people(id: [Int!]): [Person]
}

[schroeer]

I have seen now that all... query fields and my proposal to leverage the plurals have been discussed before in a pull request. I think that all... fields would be useful.