Cleanup & Fixes for .NET 5 (#309)

- [X] Fixes several bugs
- [X] Updates more ordinal issues
- [X] Cleans up the code a bit
- [X] Turns classes static that should have been
- [X] Changes TcpServer.Instances to a HashSet

Bumps release version

Projects/Server/Network/Packets/OutgoingAccountPackets.cs

@@ -15,8 +15,8 @@
 
 using System;
 using System.IO;
-using Server.Accounting;
 using System.Buffers;
+using Server.Accounting;
 
 namespace Server.Network
 {