Fixes https://github.com/neo4j-contrib/neo4j-jdbc/issues/19

This attempts to fix https://github.com/neo4j-contrib/neo4j-jdbc/issues/19

Once this issue is dealt with, users of neo4j-jdbc will need to set the property: 

```
"restlet.helperclass", "org.restlet.ext.httpclient.HttpClientHelper"
```

In order for the correct connector to work for connecting via SSL. The underlying Restlet [Engine.java](https://github.com/restlet/restlet-framework-java/blob/2.1.6/modules/org.restlet/src/org/restlet/engine/Engine.java) code it returns the order of engines in an inconsistent manner.

```java
    /**
     * Returns the list of available client connectors.
     * 
     * @return The list of available client connectors.
     */
    public List<ConnectorHelper<Client>> getRegisteredClients() {
        return this.registeredClients;
    }
```

Sometimes the httpclient engine is ranked above the internal restlet ssl engine. So, sometimes one or the other is selected. When the internal restlet ssl engine is select it causes Neo4j-jdbc to intermittently hang indefinitely on SSL connections. I'm not sure how to address this problem. I will leave it to the maintainers to come up with a solution.