Implement Core.TickCount

Convert movement, actions (lift/use), combat, and spells to use Core.TickCount and avoid DateTime caveats (performance, system time dependency, etc)
Refactor DateTime.Now to DateTime.UtcNow
Add LOS check for Iron Maiden addon

Server/World.cs

@@ -1089,7 +1089,7 @@ namespace Server {
 
 			try {
 				using ( StreamWriter op = new StreamWriter( "world-save-errors.log", true ) ) {
-					op.WriteLine( "{0}\t{1}", DateTime.Now, message );
+					op.WriteLine( "{0}\t{1}", DateTime.UtcNow, message );
 					op.WriteLine( new StackTrace( 2 ).ToString() );
 					op.WriteLine();
 				}