Refactor DatabaseOpenWidget/Dialog and Auto-Type Database unlocking.

This patch removes redundant lock widget members of the DatabaseWidget
and consolidates all unlocking functionality into a single
DatabaseOpenWidget (with the exception of KeePass1OpenWidget).
Distinction between different unlock actions is now done via a dedicated
Intent enum class instead of using individual widgets.

Further, the DatabaseUnlockDialog has been generalized so that it is
usable for unlock intents other than just Auto-Type and is now also
used for merging databases which is less confusing to the user.

The KeePassXC main window is no longer a parent of the
DatabaseUnlockDialog and has the Qt::ForeignWindow flag set, which
should cause fewer issues with Auto-Type trying to type into KeePassXC
after unlock instead of the intended target window.

In addition, its instance has been moved into the DatabaseTabWidget
class so that it is no longer bound to individual DatabaseWidgets,
potentially allowing for database selection during Auto-Type. The actual
selection has not yet been implemented, but Auto-Type has been adjusted
to use the currently selected tab instead of the first one as an
intermediary improvement.

src/gui/DatabaseOpenDialog.h

@@ -0,0 +1,64 @@
+/*
+ *  Copyright (C) 2018 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/>.
+ */
+
+#ifndef KEEPASSX_AUTOTYPEUNLOCKDIALOG_H
+#define KEEPASSX_AUTOTYPEUNLOCKDIALOG_H
+
+#include "core/Global.h"
+
+#include <QDialog>
+#include <QPointer>
+#include <QSharedPointer>
+
+class Database;
+class DatabaseWidget;
+class DatabaseOpenWidget;
+
+class DatabaseOpenDialog : public QDialog
+{
+    Q_OBJECT
+
+public:
+    enum class Intent
+    {
+        None,
+        AutoType,
+        Merge
+    };
+
+    explicit DatabaseOpenDialog(QWidget* parent = nullptr);
+    void setFilePath(const QString& filePath);
+    void setTargetDatabaseWidget(DatabaseWidget* dbWidget);
+    void setIntent(Intent intent);
+    Intent intent() const;
+    QSharedPointer<Database> database();
+    void clearForms();
+
+signals:
+    void dialogFinished(bool);
+
+public slots:
+    void complete(bool accepted);
+
+private:
+    QPointer<DatabaseOpenWidget> m_view;
+    QSharedPointer<Database> m_db;
+    QPointer<DatabaseWidget> m_dbWidget;
+    Intent m_intent = Intent::None;
+};
+
+#endif // KEEPASSX_AUTOTYPEUNLOCKDIALOG_H