Only show count for services with counts

[jaredatch]

We should consider and discuss hiding the share count span if the current button is not in admin->query_services().

https://github.com/jaredatch/Shared-Counts/blob/develop/includes/class-shared-counts-front.php#L627

Only reason that we should maybe not do this, would be if omitting this span messes up any of the themes (I'm not sure),

[countvajhula]

Thank you for this very useful and lightweight plugin!

To add to the above comment, it would also be nice if we could disable counts altogether. For instance, when we select Count Source = None in the settings menu, it may make sense to not show the counts at that point.