Save protection preferences

Now the service has the default setting "protect attachments" when you create a new message. We offer to save the settings in Cookies after changing. It will work like this:
1. The sender removes the checkbox next to "protect attachments".
2. A window pops up and offers to save the position as the default setting.
3. If the sender responds "Yes", the setting is saved in the browser's Cookies and the next time you log in to the service with this computer and browser the checkbox next to "protect attachments" will be empty. If the sender chooses "No" everything remains unchanged.