Added unit tests (all passing unfortunately)

UI improvements
Write mode still doesn't work

ModernKeePassLib.Test/Cryptography/CryptoRandomTests.cs

@@ -0,0 +1,44 @@
+using NUnit.Framework;
+using System;
+
+#if KeePassLib
+using KeePassLib.Cryptography;
+#else
+using ModernKeePassLibPCL.Cryptography;
+#endif
+
+namespace ModernKeePassLib.Test.Shared.Cryptography
+{
+  [TestFixture ()]
+  public class CryptoRandomTests
+  {
+    [Test ()]
+    public void TestAddEntropy ()
+    {
+      // just making sure it does not throw an exception
+      CryptoRandom.Instance.AddEntropy (new byte[1]);
+    }
+
+    [Test ()]
+    public void TestGetRandomBytes ()
+    {
+      const int length = 32;
+      var bytes1 = CryptoRandom.Instance.GetRandomBytes (length);
+      Assert.That (bytes1.Length, Is.EqualTo (length));
+      var bytes2 = CryptoRandom.Instance.GetRandomBytes (length);
+      Assert.That (bytes2, Is.Not.EqualTo (bytes1));
+    }
+
+    [Test ()]
+    public void TestGeneratedBytesCount ()
+    {
+      const int length = 1;
+      CryptoRandom.Instance.GetRandomBytes (length);
+      var count1 = CryptoRandom.Instance.GeneratedBytesCount;
+      CryptoRandom.Instance.GetRandomBytes (length);
+      var count2 = CryptoRandom.Instance.GeneratedBytesCount;
+      Assert.That (count2, Is.GreaterThan (count1));
+    }
+  }
+}
+