Start tracking (activities) from anywhere

[winged]

I'd like to use active tracking more using activities, but often it's not convenient anymore. It would help if we could have a button / link anywhere a task is shown to start tracking it. Possibly, it could be combined with #681 in some way: Show a modal / dialog / menu to start an activity or create a tracking record.

We already sorta have this in the activities view, but we can only start tracking activities if we did so before. I'd just like to have the ability to do so from more places than just that view

[winged]

Closing in favour of adfinis/timed#79