Hide internet services

Allow user to show/hide internet services with the preference dialog.

At the beginning I wanted to completely remove the service objects, but too many parts of code of Clementine uses the service pointers without checking if they exist. So I just remove/add them from the tree.

The two first commits contain the "feature". The last one is after a make format which modified many other files I didn't touch.

EDIT: I didn't see the conflicts. So I reverted the make format, updated my branch and re make format. It should to be ok now :)
Use `const auto&` and `shown_services.constBegin()`