Fastthreadpool

Bugfix: Add missing parameter in map-function when called with direct=False.

Add unpack_args argument to map method.
If unpack_args=True then args will be unpacked when callback function is called (default).

Add method cleanup_children for removing dead child threads.
Add parameter 'direct' to map function to be able to either run new threads which
directly get a slice of work items or queue slices of work items in the job queue.
In _submit method ensure to create new child thread if all active child threads are busy.

Unpack arguments when calling callback function in map.

Make list of child thread objects visible.
Hopefully finally fix a deadlock issue when job queue is running empty.

Add optional init_args parameter for init_callback.
Set attribute 'tnum' to child number.