Support lists with a single value in NODE_ queries

[vladar]

Some schemas do not provide any means to fetch a single node. Instead, they allow you to query a list of nodes by id (but returning a list with a single element). E.g.

query NODE_FOO {
  queryFoo(input: { id: $id }) {
    ...idFragment
  }
}

and the return value could be:

{
  data: {
    queryFoo: [ { id: 'foo' } ]
  }
}

The toolkit must support this and extract { id: 'foo' } as the node value. Right now it erroneously extracts [ { id: 'foo' } ] as a node value.

[vladar]

Fixed in 0.6.0