Introduced missing CustomData on Group and Entry

Introduce missing CustomData-attributes of KDBX4 format to allow
storing of plugin data for groups and entries - adopt Metadata to use
the same storage mechanism
Add simple view for CustomData as part of EditWidgetProperties
Tracking of CustomData-Modification using SIGNAL-SLOT update-mechanism

src/core/CustomData.cpp

@@ -0,0 +1,156 @@
+/*
+ *  Copyright (C) 2012 Felix Geyer <debfx@fobos.de>
+ *  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 "CustomData.h"
+
+CustomData::CustomData(QObject* parent)
+    : QObject(parent)
+{
+}
+
+QList<QString> CustomData::keys() const
+{
+    return m_data.keys();
+}
+
+bool CustomData::hasKey(const QString& key) const
+{
+    return m_data.contains(key);
+}
+
+QString CustomData::value(const QString& key) const
+{
+    return m_data.value(key);
+}
+
+bool CustomData::contains(const QString& key) const
+{
+    return m_data.contains(key);
+}
+
+bool CustomData::containsValue(const QString& value) const
+{
+    return m_data.values().contains(value);
+}
+
+void CustomData::set(const QString& key, const QString& value)
+{
+    bool emitModified = false;
+
+    bool addAttribute = !m_data.contains(key);
+    bool changeValue = !addAttribute && (m_data.value(key) != value);
+
+    if (addAttribute ) {
+        emit aboutToBeAdded(key);
+    }
+
+    if (addAttribute || changeValue) {
+        m_data.insert(key, value);
+        emitModified = true;
+    }
+
+    if (emitModified) {
+        emit modified();
+    }
+
+    if (addAttribute) {
+        emit added(key);
+    }
+}
+
+void CustomData::remove(const QString& key)
+{
+    emit aboutToBeRemoved(key);
+
+    m_data.remove(key);
+
+    emit removed(key);
+    emit modified();
+}
+
+void CustomData::rename(const QString& oldKey, const QString& newKey)
+{
+    if (!m_data.contains(oldKey)) {
+        Q_ASSERT(false);
+        return;
+    }
+
+    if (m_data.contains(newKey)) {
+        Q_ASSERT(false);
+        return;
+    }
+
+    QString data = value(oldKey);
+
+    emit aboutToRename(oldKey, newKey);
+
+    m_data.remove(oldKey);
+    m_data.insert(newKey, data);
+
+    emit modified();
+    emit renamed(oldKey, newKey);
+}
+
+void CustomData::copyDataFrom(const CustomData* other)
+{
+    if (*this != *other) {
+        emit aboutToBeReset();
+
+        m_data = other->m_data;
+
+        emit reset();
+        emit modified();
+    }
+}
+
+bool CustomData::operator==(const CustomData& other) const
+{
+    return (m_data == other.m_data);
+}
+
+bool CustomData::operator!=(const CustomData& other) const
+{
+    return (m_data != other.m_data);
+}
+
+void CustomData::clear()
+{
+    emit aboutToBeReset();
+
+    m_data.clear();
+
+    emit reset();
+    emit modified();
+}
+
+bool CustomData::isEmpty() const
+{
+    return m_data.isEmpty();
+}
+
+int CustomData::dataSize()
+{
+    int size = 0;
+
+    QHashIterator<QString, QString> i(m_data);
+    while (i.hasNext()) {
+        i.next();
+        size += i.key().toUtf8().size() + i.value().toUtf8().size();
+    }
+    return size;
+}