Makes gump code a little more readable (#390)

- [X] Adds a WriteAscii for individual characters
- [X] Updates gump code to use it so it is a little more readable

Projects/Server/Network/Packets/OutgoingMovementPackets.cs

@@ -14,7 +14,6 @@
  *************************************************************************/
 
 using System.Buffers;
-using System.IO;
 using System.Runtime.CompilerServices;
 
 namespace Server.Network

Projects/Server/Network/Packets/OutgoingPlayerPackets.cs

@@ -15,7 +15,6 @@
 
 using System;
 using System.Buffers;
-using System.IO;
 using System.Runtime.CompilerServices;
 
 namespace Server.Network

Projects/Server/Network/Packets/OutgoingTargetPackets.cs

@@ -13,7 +13,6 @@
  * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
  *************************************************************************/
 
-using System;
 using System.Buffers;
 using Server.Targeting;
 

Projects/Server/Network/Packets/OutgoingVendorBuyPackets.cs

@@ -15,7 +15,6 @@
 
 using System.Buffers;
 using System.Collections.Generic;
-using System.IO;
 using Server.Items;
 
 namespace Server.Network