Add DisplayDollItemSyncHandler

In a previous PR I have added the tile entity request packet handler which checks for building permissions to prevent the unauthorized player to open a DisplayDoll and see its content.

This Handler is being added to prevent *Hackers* from modifying a DisplayDoll through direct/crafted packet sending, or by sending raw byte data to the server.
In a valid enviroment, the player couldn't even get to see the content of the doll in the first place, to then try to modify it's items.

Because of this,  I do not bother with making sure the player gets their item back.

TShockAPI/TShockAPI.csproj

@@ -88,6 +88,7 @@
     <Compile Include="DB\ResearchDatastore.cs" />
     <Compile Include="DB\TileManager.cs" />
     <Compile Include="Extensions\ExceptionExt.cs" />
+    <Compile Include="Handlers\DisplayDollItemSyncHandler.cs" />
     <Compile Include="Handlers\IPacketHandler.cs" />
     <Compile Include="Handlers\NetModules\AmbienceHandler.cs" />
     <Compile Include="Handlers\NetModules\BestiaryHandler.cs" />