Add a way to use taskflow until library stabilized.

In order to encourage taskflow adoption, take a hint
from oslo-incubator and have a similar update.py script
that will allow users of taskflow to selectively pick up
flows and there dependencies for usage in there own projects.

Example run:

$ python2.6 update.py  --base cinder --dest-dir /tmp/cinder_test --primitives flow.linear_flow

Copying module 'taskflow.decorators' -> 'cinder.taskflow.decorators'
  '/tmp/cinder_test/cinder/taskflow/' (new)
  '/tmp/cinder_test/cinder/taskflow/__init__.py' (new)
  'taskflow/decorators.py' -> '/tmp/cinder_test/cinder/taskflow/decorators.py'
Copying module 'taskflow.exceptions' -> 'cinder.taskflow.exceptions'
  'taskflow/exceptions.py' -> '/tmp/cinder_test/cinder/taskflow/exceptions.py'
Copying module 'taskflow.patterns.base' -> 'cinder.taskflow.patterns.base'
  '/tmp/cinder_test/cinder/taskflow/patterns/' (new)
  '/tmp/cinder_test/cinder/taskflow/patterns/__init__.py' (new)
  'taskflow/patterns/base.py' -> '/tmp/cinder_test/cinder/taskflow/patterns/base.py'
Copying module 'taskflow.patterns.linear_flow' -> 'cinder.taskflow.patterns.linear_flow'
  'taskflow/patterns/linear_flow.py' -> '/tmp/cinder_test/cinder/taskflow/patterns/linear_flow.py'
Copying module 'taskflow.states' -> 'cinder.taskflow.states'
  'taskflow/states.py' -> '/tmp/cinder_test/cinder/taskflow/states.py'
Copying module 'taskflow.utils' -> 'cinder.taskflow.utils'
  'taskflow/utils.py' -> '/tmp/cinder_test/cinder/taskflow/utils.py'

Change-Id: Ib4e6299bdae737e2759f22b1eff35c344bb8beb2
Merge "Add a way to use taskflow until library stabilized."