Glance api to pass identity headers to registry v1

This patch introduces the send_identity_headers
config option that allows glance-api to pass auth identity
headers when making calls to the registry v1.

docImpact
Fixes bug 1199990

Change-Id: Ie5f07ed6dfeaa8428de4f79c4d40d182328e6ab4
Simulate image_locations table in simple/api.py

Currently the simple/api.py does not implement any 'image_locations'
related actions as in sqlalchemy/api.py. Actions like image_create/
image-update etc in simple/api.py does not look at making appropriate
changes in the image_locations table as it does in sqlalchemy/api.py

Change-Id: Ifae710d3d820225218ba72d7a16652b03b64a24f
Fixes: Bug #1202985
Merge "Glance api to pass identity headers to registry v1"
Merge "Simulate image_locations table in simple/api.py"