Added unit tests (all passing unfortunately)

UI improvements
Write mode still doesn't work

ModernKeePassLib.Test/Keys/CompositeKeyTests.cs

@@ -0,0 +1,34 @@
+using NUnit.Framework;
+using System;
+
+#if KeePassLib
+using KeePassLib.Keys;
+#else
+using ModernKeePassLibPCL.Keys;
+#endif
+
+namespace ModernKeePassLib.Test.Shared.Keys
+{
+  [TestFixture ()]
+  public class CompositeKeyTests
+  {
+    [Test ()]
+    public void TestGenerateKey32 ()
+    {
+      var originalKey = new byte[32];
+      var expectedKey = new byte[32] {
+        0xF0, 0xED, 0x57, 0xD5, 0xF0, 0xDA, 0xF3, 0x47,
+        0x90, 0xD0, 0xDB, 0x43, 0x25, 0xC6, 0x81, 0x2C,
+        0x81, 0x6A, 0x0D, 0x94, 0x96, 0xA9, 0x03, 0xE1,
+        0x20, 0xD4, 0x3A, 0x3E, 0x45, 0xAD, 0x02, 0x65
+      };
+      const ulong rounds = 1;
+
+      var composite = new CompositeKey ();
+      var key = composite.GenerateKey32 (originalKey, rounds);
+      Assert.That (key, Is.Not.Null);
+      var keyData = key.ReadData ();
+      Assert.That (keyData, Is.EqualTo (expectedKey));
+    }
+  }
+}