some useful cypher statements

**Is your feature request related to a problem? Please describe.**
I find it is difficult when I try to query a link list.
I searched and found some useful cypher statements which works for Neo4j.

**Describe the solution you'd like**

- UNWIND a vertex list

```
MATCH p=()-[]->()
WITH nodes(p) AS a
UNWIND a AS b
RETURN b
```

- WHERE not a relationship

```
MATCH (head)-[:edge*]->()
WHERE NOT ()-[:edge]->(head)
RETURN head
```

- list generation using IN

```
MATCH p=()-[]->()
WITH nodes(p) AS a
RETURN [x IN a | x.name]
```