Added unit tests (all passing unfortunately)

UI improvements
Write mode still doesn't work

ModernKeePassLib.Test/Keys/KcpCustomKeyTests.cs

@@ -0,0 +1,39 @@
+using NUnit.Framework;
+using System;
+
+#if KeePassLib
+using KeePassLib.Keys;
+#else
+using ModernKeePassLibPCL.Keys;
+#endif
+
+namespace ModernKeePassLib.Test.Shared.Keys
+{
+  [TestFixture ()]
+  public class KcpCustomKeyTests
+  {
+    static readonly byte[] testData = {
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+    };
+
+    [Test ()]
+    public void TestConstruct ()
+    {
+      var expectedHash = new byte[32] {
+        0xAF, 0x55, 0x70, 0xF5, 0xA1, 0x81, 0x0B, 0x7A,
+        0xF7, 0x8C, 0xAF, 0x4B, 0xC7, 0x0A, 0x66, 0x0F,
+        0x0D, 0xF5, 0x1E, 0x42, 0xBA, 0xF9, 0x1D, 0x4D,
+        0xE5, 0xB2, 0x32, 0x8D, 0xE0, 0xE8, 0x3D, 0xFC
+      };
+
+      var key = new KcpCustomKey ("test1", testData, false);
+      var keyData = key.KeyData.ReadData ();
+      Assert.That (keyData, Is.EqualTo (testData));
+
+      key = new KcpCustomKey ("test2", testData, true);
+      keyData = key.KeyData.ReadData ();
+      Assert.That (keyData, Is.EqualTo (expectedHash));
+    }
+  }
+}
+