Adding a Server Black list new feature in Settings - Advanced users.

[juanky201271]

The new servers list is really long (14 items) which is good, but maybe a user doesn't want to use at all some servers of that list, it could a good idea to have a servers black list in settings so the user can populate it with servers that can have some problems in the future.

Obviously if the user have concerns about some server always can pick another up from the list -> in this case the App only will use the selected server.

Only if the user manually change that selection to Automatic, then the App is going to use all of the servers to calculate which one is the fastest.

@zancas @Edicksonjga

IMO, I don't see the necessity of this new feature.