Tracking for specific roles only

Echoing with issue 1946050 → it's a very useful module and thanks for that too. I'm having the same issue with version 7. Our clients also wanted to track very specific events and specific roles and nothing else.

I have read through all your discussion on that issue and had a look on the other analytics modules. I agreed that using permission is a bit weird as by semantic meaning permission is somehow "allowing" someone to do something rather than bypassing/enabling/disabling the tracking. Also I agreed that hardcoding $user->uid == 0 rather than implementing $user->roles is a bit risky and not quite conforming best practices. That's why I tried implementing a setting section in admin form of mixpanel with some checkboxes.

I think it's a worth to have feature that could keep mixpanel data clean and quite a lot of other analytics modules have already adopted the idea.

I'll attach a patch for discussion.