Add autolock feature for synchronized root folder

Add autolock feature for synchronize root folder.
Idea is to list the opened files in the main menu, see screenshot "Autolock_1".
When you select the new menu entry, all opened files are listed, see screenshot "Autolock_2"
If the user clicks on a file, the file will be locked server side. It will be unlocked as soon as the file will be closed. See screenshot "Autolock_3".