Pull out KDFs into their own class hierarchy

In preparation for multiple KDFs in KDBX 4

src/crypto/kdf/Kdf.cpp

@@ -0,0 +1,86 @@
+/*
+ *  Copyright (C) 2017 KeePassXC Team
+ *
+ *  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 "Kdf.h"
+#include "Kdf_p.h"
+
+#include <QThread>
+#include <QElapsedTimer>
+#include <QtConcurrent>
+
+Kdf::Field::Field(quint32 id, const QString& name, quint64 min, quint64 max, bool benchmark)
+        : m_id(id)
+          , m_name(name)
+          , m_min(min)
+          , m_max(max)
+          , m_benchmark(benchmark)
+{
+}
+
+quint32 Kdf::Field::id() const
+{
+    return m_id;
+}
+
+QString Kdf::Field::name() const
+{
+    return m_name;
+}
+
+quint64 Kdf::Field::min() const
+{
+    return m_min;
+}
+
+quint64 Kdf::Field::max() const
+{
+    return m_max;
+}
+
+bool Kdf::Field::benchmarked() const
+{
+    return m_benchmark;
+}
+
+int Kdf::benchmark(int msec) const
+{
+    BenchmarkThread thread1(msec, this);
+    BenchmarkThread thread2(msec, this);
+
+    thread1.start();
+    thread2.start();
+
+    thread1.wait();
+    thread2.wait();
+
+    return qMin(thread1.rounds(), thread2.rounds());
+}
+
+Kdf::BenchmarkThread::BenchmarkThread(int msec, const Kdf* kdf)
+        : m_msec(msec)
+          , m_kdf(kdf)
+{
+}
+
+int Kdf::BenchmarkThread::rounds()
+{
+    return m_rounds;
+}
+
+void Kdf::BenchmarkThread::run() {
+    m_rounds = m_kdf->benchmarkImpl(m_msec);
+}