Added unit tests (all passing unfortunately)

UI improvements
Write mode still doesn't work

ModernKeePassLib.Test/Cryptography/CryptoRandomStreamTests.cs

@@ -0,0 +1,60 @@
+using NUnit.Framework;
+using System;
+
+#if KeePassLib
+using KeePassLib.Cryptography;
+#else
+using ModernKeePassLibPCL.Cryptography;
+#endif
+
+namespace ModernKeePassLib.Test.Shared.Cryptography
+{
+  [TestFixture ()]
+  public class CryptoRandomStreamTests
+  {
+    void TestGetRandomBytes(CryptoRandomStream stream)
+    {
+      const uint length = 16;
+      var bytes1 = stream.GetRandomBytes (length);
+      Assert.That (bytes1.Length, Is.EqualTo (length));
+      var bytes2 = stream.GetRandomBytes (length);
+      Assert.That (bytes2, Is.Not.EqualTo (bytes1));
+    }
+
+    [Test ()]
+    public void TestGetRandomBytesCrsAlgorithmSalsa20 ()
+    {
+      var stream = new CryptoRandomStream (CrsAlgorithm.Salsa20, new byte[16]);
+      TestGetRandomBytes (stream);
+    }
+
+    [Test ()]
+    public void TestGetRandomBytesCrsAlgorithmArcFourVariant ()
+    {
+      var stream = new CryptoRandomStream (CrsAlgorithm.ArcFourVariant, new byte[16]);
+      TestGetRandomBytes (stream);
+    }
+
+    void TestGetRandomInt64 (CryptoRandomStream stream)
+    {
+      var value1 = stream.GetRandomUInt64 ();
+      var value2 = stream.GetRandomUInt64 ();
+      Assert.That (value2, Is.Not.EqualTo (value1));
+    }
+
+    [Test ()]
+    public void TestGetRandomInt64AlgorithmSalsa20 ()
+    {
+      var stream = new CryptoRandomStream (CrsAlgorithm.Salsa20, new byte[16]);
+      TestGetRandomInt64 (stream);
+    }
+
+    [Test ()]
+    public void TestGetRandomInt64AlgorithmArcFourVariant ()
+    {
+      var stream = new CryptoRandomStream (CrsAlgorithm.ArcFourVariant, new byte[16]);
+      TestGetRandomInt64 (stream);
+    }
+  }
+}
+