[Qt] add option to allow self signed root certs (for testing)

- it is helpful to be able to test and verify payment request processing
  by allowing self signed root certificates (e.g. generated by Gavins
  "certificate authority in a box")
- This option is just shown in the UI options, if -help-debug is enabled.

src/qt/utilitydialog.cpp

@@ -12,6 +12,7 @@
 
 #include "clientversion.h"
 #include "init.h"
+#include "util.h"
 
 #include <stdio.h>
 
@@ -108,6 +109,12 @@ HelpMessageDialog::HelpMessageDialog(QWidget *parent, bool about) :
         cursor.movePosition(QTextCursor::NextRow);
         cursor.insertText(tr("UI options") + ":", bold);
         cursor.movePosition(QTextCursor::NextRow);
+        if (GetBoolArg("-help-debug", false)) {
+            cursor.insertText("-allowselfsignedrootcertificates");
+            cursor.movePosition(QTextCursor::NextCell);
+            cursor.insertText(tr("Allow self signed root certificates (default: 0)"));
+            cursor.movePosition(QTextCursor::NextCell);
+        }
         cursor.insertText("-choosedatadir");
         cursor.movePosition(QTextCursor::NextCell);
         cursor.insertText(tr("Choose data directory on startup (default: 0)"));