Use WalletSeed.DecodeAndValidateUserInput for backup confirmation.

This allows proceeding to create the wallet when either the
hexadecimal or PGP word list encoding of the seed is entered in the
backup confirmation dialog.

Paymetheus/StartupWizard.cs

@@ -181,7 +181,7 @@ private void Continue()
 
                 if (CreateChecked)
                 {
-                    Wizard.CurrentDialog = new ConfirmSeedBackupDialog(Wizard, _randomSeed, this);
+                    Wizard.CurrentDialog = new ConfirmSeedBackupDialog(Wizard, this, _randomSeed, _pgpWordList);
                 }
                 else
                 {
@@ -202,35 +202,49 @@ private void Continue()
 
     sealed class ConfirmSeedBackupDialog : ConnectionWizardDialog
     {
-        public ConfirmSeedBackupDialog(StartupWizard wizard, byte[] seed, CreateOrImportSeedDialog previousDialog)
+        public ConfirmSeedBackupDialog(StartupWizard wizard, CreateOrImportSeedDialog previousDialog,
+            byte[] seed, PgpWordList pgpWordlist)
             : base(wizard)
         {
-            _seed = seed;
             _previousDialog = previousDialog;
+            _seed = seed;
+            _pgpWordList = pgpWordlist;
 
             ConfirmSeedCommand = new DelegateCommand(ConfirmSeed);
             BackCommand = new DelegateCommand(Back);
         }
 
-        private byte[] _seed;
         private CreateOrImportSeedDialog _previousDialog;
+        private byte[] _seed;
+        private PgpWordList _pgpWordList;
 
         public string Input { get; set; } = "";
 
         public DelegateCommand ConfirmSeedCommand { get; }
         private void ConfirmSeed()
         {
-            byte[] decodedSeed;
-            if (Hexadecimal.TryDecode(Input, out decodedSeed))
+            try
             {
+                ConfirmSeedCommand.Executable = false;
+
+                var decodedSeed = WalletSeed.DecodeAndValidateUserInput(Input, _pgpWordList);
                 if (ValueArray.ShallowEquals(_seed, decodedSeed))
                 {
                     _wizard.CurrentDialog = new PromptPassphrasesDialog(Wizard, _seed);
-                    return;
+                }
+                else
+                {
+                    MessageBox.Show("Seed does not match");
                 }
             }
-
-            MessageBox.Show("Seed does not match");
+            catch (Exception ex)
+            {
+                MessageBox.Show(ex.Message, "Invalid seed");
+            }
+            finally
+            {
+                ConfirmSeedCommand.Executable = true;
+            }
         }
 
         public DelegateCommand BackCommand { get; }