[TI-44] Make "timew stop" switch currently active task in Taskwarrior switch to "inactive"

_Frédéric Meynadier on 2016-09-05T08:39:39Z says:_

As discussed in https://groups.google.com/forum/#!topic/taskwarrior-dev/KoOxlr30ZXc , this is a suggestion to implement a two-way integration with Taskwarrior.

Currently, "task 42 start" makes the task active in Taskwarrior and starts tracking it in Timewarrior thanks to the appropriate hook. "task 42 stop" makes it inactive, and stops timetracking.

But it would also seem natural that "timew stop" stops timetracking in Timewarrior (which it does) *and* switches the currently active task to "inactive" in Taskwarrior, provided there's no ambiguity (which should be the case as long as we don't have overlapping tags). This would avoid the need to provide a task ID.

In the discussion, Paul states that an appropriate way to implement it will be the foreseen "rules" mechanism.