Add /v1/tasks to list tasks, and kill them per app and host

List all tasks:

    curl localhost:8080/v1/tasks

Kill all tasks of app *sleep* on host *gob*:

    curl -X POST 'localhost:8080/v1/tasks/kill?host=gob&appId=sleep'

Kill all tasks of app *sleep* on all hosts:

    curl -X POST 'localhost:8080/v1/tasks/kill?host=*&appId=sleep'