Sqlite secure delete

Fixes #102

src/class_sqlThread.py

@@ -25,6 +25,8 @@ class sqlThread(threading.Thread):
         self.conn = sqlite3.connect(shared.appdata + 'messages.dat')
         self.conn.text_factory = str
         self.cur = self.conn.cursor()
+        
+        self.cur.execute('PRAGMA secure_delete = true')
 
         try:
             self.cur.execute(