added TrainingZoneMessage packet; rudimentary comments, but no tests

common/src/main/scala/net/psforever/packet/GamePacketOpcode.scala

@@ -457,7 +457,7 @@ object GamePacketOpcode extends Enumeration {
     case 0x72 => noDecoder(FriendsRequest)
     case 0x73 => noDecoder(FriendsResponse)
     case 0x74 => noDecoder(TriggerEnvironmentalDamageMessage)
-    case 0x75 => noDecoder(TrainingZoneMessage)
+    case 0x75 => game.TrainingZoneMessage.decode
     case 0x76 => noDecoder(DeployableObjectsInfoMessage)
     case 0x77 => noDecoder(SquadState)
     // 0x78

common/src/main/scala/net/psforever/packet/game/TrainingZoneMessage.scala

@@ -0,0 +1,38 @@
+// Copyright (c) 2016 PSForever.net to present
+package net.psforever.packet.game
+
+import net.psforever.packet.{GamePacketOpcode, Marshallable, PlanetSideGamePacket}
+import scodec.Codec
+import scodec.codecs._
+
+/**
+  * The client is telling the server that the player wants to go to the training zones.<br>
+  * <br>
+  * This message is dispatched when a player enters the VR hallway / VR teleport and accepts the "Shooting Range" or the "Vehicle Training Area" options on the prompt.
+  * The packet sends indication to the server (as if it didn't know?) in regards to which training grounds the player should be sent.
+  * Players are sent to their respective empire's area by default.<br>
+  * @param unk1 na;
+  *             19 (`13`) when shooting range;
+  *             22 (`16`) when ground vehicle range
+  * @param unk2 na; always zero?
+  * @param unk3 na; always zero?
+  * @param unk4 na; always zero?
+  */
+final case class TrainingZoneMessage(unk1 : Int,
+                                     unk2 : Int,
+                                     unk3 : Int,
+                                     unk4 : Int)
+  extends PlanetSideGamePacket {
+  type Packet = TrainingZoneMessage
+  def opcode = GamePacketOpcode.TrainingZoneMessage
+  def encode = TrainingZoneMessage.encode(this)
+}
+
+object TrainingZoneMessage extends Marshallable[TrainingZoneMessage] {
+  implicit val codec : Codec[TrainingZoneMessage] = (
+      ("unk1" | uint8L) ::
+        ("unk2" | uint8L) ::
+        ("unk3" | uint8L) ::
+        ("unk4" | uint8L)
+    ).as[TrainingZoneMessage]
+}