Added option --enable-logging to enable diagnostic logging (#106)

* Added option --enable-logging to enable diagnostic logging

* Addressing feedback

* Addressing feedback, round 2

test/Microsoft.SqlTools.ServiceLayer.Test/Utility/CommandOptionsTests.cs

@@ -0,0 +1,69 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+using Microsoft.SqlTools.ServiceLayer.Utility;
+using Xunit;
+
+namespace Microsoft.SqlTools.Test.Utility
+{
+    /// <summary>
+    /// Tests for the CommandOptions class
+    /// </summary>
+    public class CommandOptionsTests
+    {
+        [Fact]
+        public void LoggingEnabledWhenFlagProvided()
+        {
+            var args = new string[] {"--enable-logging"};
+            CommandOptions options = new CommandOptions(args);
+            Assert.NotNull(options);
+
+            Assert.True(options.EnableLogging);
+            Assert.False(options.ShouldExit);
+        }
+
+        [Fact]
+        public void LoggingDisabledWhenFlagNotProvided()
+        {
+            var args = new string[] {};
+            CommandOptions options = new CommandOptions(args);
+            Assert.NotNull(options);
+
+            Assert.False(options.EnableLogging);
+            Assert.False(options.ShouldExit);
+        }
+
+        [Fact]
+        public void UsageIsShownWhenHelpFlagProvided()
+        {
+            var args = new string[] {"--help"};
+            CommandOptions options = new CommandOptions(args);
+            Assert.NotNull(options);
+
+            Assert.True(options.ShouldExit);
+        }
+
+        [Fact]
+        public void UsageIsShownWhenBadArgumentsProvided()
+        {
+            var args = new string[] {"--unknown-argument", "/bad-argument"};
+            CommandOptions options = new CommandOptions(args);
+            Assert.NotNull(options);
+
+            Assert.True(options.ShouldExit);
+        }
+
+        [Fact]
+        public void DefaultValuesAreUsedWhenNoArgumentsAreProvided()
+        {
+            var args = new string[] {};
+            CommandOptions options = new CommandOptions(args);
+            Assert.NotNull(options);
+
+            Assert.False(options.EnableLogging);
+            Assert.False(options.ShouldExit);
+        }
+    }
+}