Expose checksum index image property in client

Implement checksum image index property in the python-glanceclient

Change-Id: If1426b7938457014ef27a86d3902d53854161627
Implements: blueprint index-using-checksum-image-property
Pass all identity headers received to glance

There is an upcoming patch in nova which passes identity
headers to glance client. We want to ensure that these get
passed to glance, which in turn with help the no auth
option in glance.

Resolves bug 1200761

Change-Id: Ifbef582aa4e64a2e7a46db43a9cc6cf8c3531dbd
Merge "Expose checksum index image property in client"
Merge "Pass all identity headers received to glance"