Develop initial implementation

The initial implementation can be very simple ... I'm imagining DOs as the basic KeyValue storage mechanism, along with the Edge (relationship) and auto-generated reverse edge like:
```
"thingABC.prop: myValue -> id1234": "https://graph.do/whateverType/id1234"
"whateverType: id1234 <- myValue": "https://graph.do/otherType/thingABC"
```

