Disable "Run Diagnostics" for non-running apps/services

Created by: JoKeyser

This should fix issue #829 (closed), see there for more reasoning.

It may seem a bit silly to implement this by adding an entire template just for a disabled button. I first tried to check if an app is running in the button's template (see 1st commit), but that's impossible since it gets included from multiple places, among them the Users page, and also Tor is a special case. That's why I ended up with this solution.

Now it's a straight-forward implementation: Adding a disabled button, and switching in each module that includes it.

If you agree to merge, please don't forget to squash the commits; sorry for the mess.