Move deleted pages to a "trash" folder

Yet another feature request for the sake of protecting content from careless deletions. :)

It could be interesting to change the the `taskRemove` implementation to (perhaps optionally) move the page's folder to a "trash" folder, perhaps in `user/trash` or `user/pages/.trash`.

This could be fairly easy to do when deleting the whole folder. When deleting a translation, it might be harder I guess.

This wouldn't be a small implementation since there would need to be a trash view, a restore option, messages for success and for "can't restore because X", etc.