Allow for multiple queries inside of a GraphQL API request

[deekerno]

Currently, our GraphQL API does not allow for multiple queries inside of the body of a request. For example, the following request will not succeed despite being totally valid GraphQL functionality:

query {
    block {
        id
    }
}

query {
    tx {
        id
    }
}

We should amend the API response to allow for multiple query result sets.