Manager now sends out task updates via SocketIO, and the web interface
handles those.
Note that there is a `BroadcastTaskUpdate()` function, but not a
`BroadcastNewTask`. The 'new job' broadcast is sent after the job's
tasks have been created, and thus there is no need for a separate
broadcast per task.
Direct copy of the Flamenco Server Python code, for handling the change
of a job's status to trigger status changes on its tasks.
Not yet connected to the rest of the Manager logic.
The task status change → job status change code is a direct port of the
Flamenco Server v2 code written in Python.
There is no job status change → task status changes logic yet, and the
tests are also far from complete.
