Add option to hide menu items for disabled watchers

[rickiewars]

Implementation for this feature request

I have some watchers disabled because I do not use them that often.
I would like to be able to hide the respective navigation items.
This pull request implements that.
It makes the sidebar a bit less cluttered if you only use a handfull of watchers.

I've implemented this feature as an opt-in feature using a config parameter.
Only if the hide_disabled_watcher_pages config is true and if the corosponding watcher is disabled, the menu item will be hidden.

Please let me know if anything needs to be changed.

[taylorotwell]

Thanks for your pull request to Laravel!

Unfortunately, I'm going to delay merging this code for now. To preserve our ability to adequately maintain the framework, we need to be very careful regarding the amount of code we include.

If applicable, please consider releasing your code as a package so that the community can still take advantage of your contributions!