Correct multiple issues with database saving

* Mark the database as clean after fully completing the file save operation INSTEAD of when merely writing the database to a file.

* Stop the modified timer when marking the database as clean, this prevents latent erroneous modified signals from being emitted.

* Do not restart the modified timer after a new change is detected while it is still running.

src/core/Database.h

@@ -21,9 +21,9 @@
 
 #include <QDateTime>
 #include <QHash>
-#include <QObject>
 #include <QPointer>
 #include <QScopedPointer>
+#include <QTimer>
 
 #include "config-keepassx.h"
 #include "crypto/kdf/AesKdf.h"
@@ -37,7 +37,6 @@ enum class EntryReferenceType;
 class FileWatcher;
 class Group;
 class Metadata;
-class QTimer;
 class QIODevice;
 
 struct DeletedObject
@@ -155,9 +154,6 @@ signals:
     void databaseDiscarded();
     void databaseFileChanged();
 
-private slots:
-    void startModifiedTimer();
-
 private:
     struct DatabaseData
     {
@@ -211,7 +207,7 @@ private:
     DatabaseData m_data;
     QPointer<Group> m_rootGroup;
     QList<DeletedObject> m_deletedObjects;
-    QPointer<QTimer> m_timer;
+    QTimer m_modifiedTimer;
     QPointer<FileWatcher> m_fileWatcher;
     bool m_initialized = false;
     bool m_modified = false;