embedded: server builder now supports setting protocol version

[hjizettle]

If not supplied the ProtocolVersion.NEWEST_SUPPORTED will be used in order to maintain backwards compatibility.

Fixes: #374

[doanduyhai]

Achilles 6.1.0 is just released, it will be available soon on Maven central

[doanduyhai]

 CassandraEmbeddedServerBuilder
        .builder()
        .withConnectionProtocol(ProtocolVersion.V4)    
         ...
        .buildNativeSession() || buildNativeCluster() || buildServer();

        @Rule
    public AchillesTestResource<ManagerFactory> resource =  AchillesTestResourceBuilder
        .forJunit()
        .withProtocolVersion(ProtocolVersion.V4)
        .
        ...
        .build((cluster, statementsCache) -> ManagerFactoryBuilder
            .builder(cluster)
            .doForceSchemaCreation(true)
            .withStatementCache(statementsCache) //MANDATORY
            .withDefaultKeyspaceName("achilles_embedded")
            .build()
        );