Fix #633 - Support _class as a node label property

We currently support `_type` as a node label property
for entities that are created by the Neo4j store. In
order to perform more abstract queries, we also need
to add `_class`.

Example query by `_type`:

```cy
MATCH (account:github_account)-[OWNS]->
  (repo:github_repo)-[ALLOWS]->
  (user:github_user {
    role:"OUTSIDE"
  })
RETURN account, repo, user
```

Example query by `_class`:

```cy
MATCH (account:Account)-[OWNS]->
  (repo:CodeRepo)-[ALLOWS]->
  (user:User {
    role:"OUTSIDE"
  })
RETURN account, repo, user
```

packages/integration-sdk-cli/src/neo4j/neo4jGraphStore.ts

@@ -64,7 +64,8 @@ export class Neo4jGraphStore {
       const buildCommand = `
         MERGE (${nodeAlias} {_key: $finalKeyValue, _integrationInstanceID: $integrationInstanceID}) 
         SET ${nodeAlias} += $propertyParameters
-        SET ${nodeAlias}:${entity._type};`;
+        SET ${nodeAlias}:${entity._type}
+        SET ${nodeAlias}:${entity._class};`;
       await this.runCypherCommand(buildCommand, {
         propertyParameters: propertyParameters,
         finalKeyValue: finalKeyValue,