Replace properties is not supported

**Describe the bug**
The following query will failed:
```cypher
MERGE (n:Project { name: $name })
SET n = $properties
RETURN n
```
while `$properties` is a map.

The following error occured:
`
error: SET clause expects a variable name
`

This is possible with neo4j https://neo4j.com/docs/cypher-manual/current/clauses/set/#set-replace-properties-using-map

**How are you accessing AGE (Command line, driver, etc.)?**
nodejs pg.

**Environment (please complete the following information):**
- Version: 1.1.0

**Additional context**
Do we have alternative way of doing this? Rather than query the whole node and iterate all properties in code, delete property one by one and then set them to the new values.

#343 seems the same issue.