Synced jsonutils from oslo-incubator

The sync includes change that drastically enhances performance on Python
2.6 with fresh simplejson library installed.

Included commits:
* jsonutils.py:
  - 1b901885: Enforce unicode json output for jsonutils.load[s]()
  - cd909d83: jsonutils.load() accepts file pointer, not string
  - d14f56f0: On Python <= 2.6, use simplejson if available

This change also introduces new incubator module 'strutils' that is used
by jsonutils now.

Change-Id: Ief94101488214ddf93c3547a9c50134826b9b165
Closes-Bug: 1314129
Merge "Synced jsonutils from oslo-incubator" into stable/icehouse