Implement a hide button to avoid accidental deletion of important emails

[yanpelov]

When you have hundreds of threads in the table there might be ones you don't want to delete or move to trash. For example, I have 20 emails from my friend in one thread or from a shop where I was buying sth and I don't want to lose them by accident. If you go through a long list, it could be useful to have the ability to remove this row from the table without deleting messages. Maybe save button. Next to delete buttons.