Merging to .NET Core 3.1 (#2)

* Code refactoring

* Rebuilt project for .NET Core 3.1

* Updated code comments

GZipTest/IProcessingModule.cs

@@ -1,18 +1,20 @@
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace GZipTest
+namespace GZipTest
 {
-    interface IProcessingModule
-    {
-        void Run(string input, string output);
-        void Stop();
-        event ProgressChangedEventHandler ProgressChanged;
-        event EventHandler Complete;
-        event ErrorEventHandler ErrorOccured;
-    }
-}
+	/// <summary>
+	/// Processing module interface
+	/// </summary>
+	interface IProcessingModule
+	{
+		/// <summary>
+		/// Indicates wether the module is processing a file
+		/// </summary>
+		bool IsWorking { get; }
+
+		/// <summary>
+		/// Starts the job
+		/// </summary>
+		/// <param name="input">Source file path (relative or absolute)</param>
+		/// <param name="output">Destination file path (relative or absolute)</param>
+		void Run(string input, string output);
+	}
+}