Oslo Service Workers for Windows

Currently, oslo_service project has a couple of Linux specific implementations, which makes it impossible to use under Windows. A few examples would be service.ProcessLauncher, which uses:

* eventlet.greenio.GreenPipe, which it cannot be used, as it tries to set the pipe as non-blocking, mechanism that does not exist in Windows. [1]
* os.fork, which does not exist in Windows. [2]

An alternative option for forking would be spawning subprocesses by using the multiprocessing module, which avoids the GIL problem. [3]

The purpose of this blueprint is to implement an alternative way to spawn service workers, which will work for OpenStack services on Windows.

[1] http://paste.openstack.org/show/284115/
[2] https://docs.python.org/2/library/os.html#os.fork
[3] http://sebastianraschka.com/Articles/2014_multiprocessing_intro.html