Add "No found games" message to configurator

[lilyremigia]

On the find games screen of the configuration, there should be a "no found games", when the result is empty.
The user may think the program did nothing or is being extremely slow otherwise.

[brliron]

Note: this should only happen as a result of the user pressing a scan button, not for the automatic scan that we run when entering this screen.

[lilyremigia]

@brliron See #238