Implements KDBX4 format with Argon2 KDF

* Adds KDBX4 reader/writer interfaces
* Adds KDBX4 XML reader/write interfaces
* Implements test cases for KDBX4
* Fully compatible with KeePass2
* Corrects minor issues with Argon2 KDF

tests/TestKdbx4XmlReader.cpp

@@ -0,0 +1,22 @@
+/*
+ *  Copyright (C) 2017 KeePassXC Team <team@keepassxc.org>
+ *
+ *  This program is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 2 or (at your option)
+ *  version 3 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <QTest>
+
+#include "TestKeePass2XmlReader.h"
+
+QTEST_GUILESS_MAIN(TestKdbx4XmlReader)