fix(net): Clean up for mobile packets (#338)

### Breaking Change
- [X] `Mobile.GetOldPacketFlags()` no longer exists. Instead there is a flag for `Mobile.GetPacketFlags()`.

### Non-Breaking Changes
- [X] Consolidates move to world for mobiles
- [X] Consolidates mobile packets between stygian abyss and older

This PR supersedes changes in #337. That PR will need to be redone and broken out anyway.

Projects/UOContent/Commands/VisibilityList.cs

@@ -118,7 +118,7 @@ namespace Server.Commands
                             {
                                 if (targ.CanSee(pm))
                                 {
-                                    ns.Send(MobileIncoming.Create(ns, targ, pm));
+                                    ns.Send(new MobileIncoming(ns, targ, pm));
 
                                     pm.SendOPLPacketTo(ns);