Add events to GraphQL endpoint

[ivankocienski]

You can now query the API with things like this for event index:

query {
    allEvents {
        id
        summary
        description
    }
}

And this for show event:

query {
    event(id:123) {
        id
        summary
        description
        address {
            streetAddress
            city
            postcode
        }
    }
}

[kimadactyl]

Looks great. I'd like to add in neighbourhood info to the address but we can put that in a future PR