Updates Serialization (#292)

- [X] Removes all save strategies
- [X] Removes duplicate file writer that won't be used
- [X] Removes persistence (it will become a duplicate system)
- [X] Add a save position variable to skip serializing a clean item/mobile
- [X] Update Guilds/Accounts to be IEntity types
    - Because guilds are abstract, this may make serialization tricky.
- [X] Update the generalized IEntity writing
- [X] Update the load/save to write to buffers then to files in background


Bumps release version

Projects/Server.Tests/Network/Packets/Old/Outgoing/VendorSellPacketTests.cs

@@ -15,9 +15,9 @@ namespace Server.Tests.Network
             var vendor = new Mobile(0x1);
             vendor.DefaultMobileInit();
 
-            var item1 = new Item(Serial.LastItem + 1);
-            var item2 = new Item(Serial.LastItem + 2) { Name = "Second Item" };
-            var item3 = new Item(Serial.LastItem + 3);
+            var item1 = new Item(World.NewItem);
+            var item2 = new Item(World.NewItem) { Name = "Second Item" };
+            var item3 = new Item(World.NewItem);
 
             var sellStates = new List<SellItemState>
             {