More functions for the "content" tab

[subcor]

There are two functions that I'd find useful:
- autorefresh the content tab when there are changes (for example if it's sorted by download priority and you add/remove a file you have to force a refresh by click to an other tab and back)
- a new option(s) for the right click menu; expand all subfolders and contract all subfolders

[Nemo]

You can open a new issue here and label it with [Wishlist] if you want, it gets more attention over there.