Allow traversing upwards in the graph

[jepp2078]

We need to add the ability to traverse up the graph.

To do this we need to add the parent objects to the schema.graphql file.

Eg. for a meetup

type Meetup {
   id: Int!
   name: String
   date: String
   duration: String
   attendees: Int
   address: String
   sponsors: MeetupSponsor
   presentations: [Presentation]
   meetupGroup: MeetupGroup
}

When this is done, make generate can be run, and a resolver then needs to be implemented in the meetupResolver.