Remove uses of ApplicationException (#334)

Co-authored-by: Andrii Siriak <siryaka@gmail.com>

Author: reima

Algorithms/Search/AStar/PathfindingException.cs

@@ -5,7 +5,7 @@ namespace Algorithms.Search.AStar
     /// <summary>
     ///     A pathfinding exception is thrown when the Pathfinder encounters a critical error and can not continue.
     /// </summary>
-    public class PathfindingException : ApplicationException
+    public class PathfindingException : Exception
     {
         public PathfindingException(string message)
             : base(message)

Utilities/Exceptions/ItemNotFoundException.cs

@@ -5,7 +5,7 @@ namespace Utilities.Exceptions
     /// <summary>
     ///     Signs that sequence doesn't contain any items that one was looking for.
     /// </summary>
-    public class ItemNotFoundException : ApplicationException
+    public class ItemNotFoundException : Exception
     {
     }
 }