Do not use variables to add edges to make code more portable (i.e. Comsoms DB)

and code more declarative

```
gremlin> p = graph.addVertex(label, "product",
                   "name", "Red Gremlin Jacket")
==>v[3]
gremlin>
gremlin> p.addEdge("inCategory", c)
```

it is easy to add edge by getting vertex by name and then adding edge.

people would find out variables themselves (or provide 2 variants with and without variables)