use traversal to add vertex, mostly to fix remote graph setups

when using remote graphs, Graph is actually just an empty shell and
can't be used to e.g. add elements.

open problems:
* marshalled classes can use the @id annotation to specify
the ID of a vertex, but we cannot set the id of a vertex inside a traversal
* same needs to be applied for edges

re #223

gremlin-scala/src/main/scala/gremlin/scala/ScalaGraph.scala

@@ -18,21 +18,22 @@ case class ScalaGraph(traversalSource: TraversalSource) {
   def configure(conf: TraversalSource => TraversalSource) =
     ScalaGraph(conf(TraversalSource(graph)))
 
-  def addVertex(label: String): Vertex = graph.addVertex(label)
+  def addVertex(): Vertex =
+    traversalSource.underlying.addV().next
 
-  def addVertex(): Vertex = graph.addVertex()
+  def addVertex(label: String): Vertex =
+    traversalSource.underlying.addV(label).next
 
-  def addVertex(label: String, properties: (String, Any)*): Vertex = {
-    val labelParam = Seq(T.label, label)
-    val params =
-      properties.flatMap(pair => Seq(pair._1, pair._2.asInstanceOf[AnyRef]))
-    graph.addVertex(labelParam ++ params: _*)
+  def addVertex(properties: (String, Any)*): Vertex = {
+    val traversal = traversalSource.underlying.addV()
+    properties.foreach { case (key, value) => traversal.property(key, value) }
+    traversal.next
   }
 
-  def addVertex(properties: (String, Any)*): Vertex = {
-    val params =
-      properties.flatMap(pair => Seq(pair._1, pair._2.asInstanceOf[AnyRef]))
-    graph.addVertex(params: _*)
+  def addVertex(label: String, properties: (String, Any)*): Vertex = {
+    val traversal = traversalSource.underlying.addV(label)
+    properties.foreach { case (key, value) => traversal.property(key, value) }
+    traversal.next
   }
 
   def addVertex(label: String, properties: Map[String, Any]): Vertex =
@@ -44,10 +45,13 @@ case class ScalaGraph(traversalSource: TraversalSource) {
   /**
     * Save an object's values into a new vertex
     * @param cc The case class to persist as a vertex
+    *
+    * Note: this doesn't work with remote graphs, since remote graphs require you to use
+    * traversal steps to add a vertex (e.g. addV), but there's no step to set the ID
     */
   def addVertex[CC <: Product: Marshallable](cc: CC): Vertex = {
     val fromCC = implicitly[Marshallable[CC]].fromCC(cc)
-    val idParam = fromCC.id.toSeq.flatMap(List(T.id, _))
+    val idParam = fromCC.id.toSeq.flatMap(List(T.id, _)) //TODO: this will break things
     val labelParam = Seq(T.label, fromCC.label)
     val params = fromCC.valueMap.toSeq.flatMap(pair => Seq(pair._1, pair._2.asInstanceOf[AnyRef]))
     graph.addVertex(idParam ++ labelParam ++ params: _*)
@@ -60,34 +64,37 @@ case class ScalaGraph(traversalSource: TraversalSource) {
   def +(label: String, properties: KeyValue[_]*): Vertex =
     addVertex(label, properties.map(v => (v.key.name, v.value)).toMap)
 
+  /** start a traversal with `addV` */
   @deprecated("use `traversal.addV`", "3.3.1.2")
   def addV(): GremlinScala.Aux[Vertex, HNil] =
     traversalSource.addV()
 
+  /** start a traversal with `addV` */
   @deprecated("use `traversal.addV`", "3.3.1.2")
   def addV(label: String): GremlinScala.Aux[Vertex, HNil] =
     traversalSource.addV(label)
 
   @deprecated("use `traversal.inject`", "3.3.1.2")
+  /** start a traversal with given `starts`` */
   def inject[S](starts: S*): GremlinScala.Aux[S, HNil] =
     traversalSource.inject(starts: _*)
 
-  // start traversal with all vertices
+  /** start traversal with all vertices */
   @deprecated("use `traversal.V`", "3.3.1.2")
   def V(): GremlinScala.Aux[Vertex, HNil] =
     traversalSource.V()
 
-  // start traversal with all edges
+  /** start traversal with all edges */
   @deprecated("use `traversal.E`", "3.3.1.2")
   def E(): GremlinScala.Aux[Edge, HNil] =
     traversalSource.E()
 
-  // start traversal with some vertices identified by given ids
+  /** start traversal with some vertices identified by given ids */
   @deprecated("use `traversal.V`", "3.3.1.2")
   def V(vertexIds: Any*): GremlinScala.Aux[Vertex, HNil] =
     traversalSource.V(vertexIds: _*)
 
-  // start traversal with some edges identified by given ids
+  /** start traversal with some edges identified by given ids */
   @deprecated("use `traversal.E`", "3.3.1.2")
   def E(edgeIds: Any*): GremlinScala.Aux[Edge, HNil] =
     traversalSource.E(edgeIds: _*)

gremlin-scala/src/test/scala/gremlin/scala/ElementSpec.scala

@@ -42,7 +42,7 @@ class ElementSpec extends TestBase {
       * TODO: `properties` should take `Key` as well
       */
     it("sets a property with multiple values") {
-      val v = graph.addV().property(Name, "marko").property(Name, "marko a. rodriguez").head
+      val v = graph.addVertex((Name.name -> "marko"), (Name.name -> "marko a. rodriguez"))
       graph.V(v).properties(Name.name).count.head shouldBe 2
 
       v.property(Cardinality.list, Name.name, "m. a. rodriguez")