Add support for extension list

 - Add support in the common section for extension list. This only
   supports Identity for now. Once the APIs for volume and compute
   are supported in the respective APIs, they will be added. Once
   network is added to this client, it will be added (the API already
   supports it).
 - Include extension fakes for volume and compute for pre-enablement.

Change-Id: Iebb0156a779887d2ab06488a2a27b70b56369376
Closes-Bug: #1319115
Ignore most of the new hacking 0.9.2 rules

So we can update requriements.txt.  But fix a couple of easy ones:
* Fix E251 (1 occurrance)
* Fix E131 (1 occurrance)

Change-Id: I62aaa423aa6da9e9f0ca026ec586b51cc6a6df03
Updated from global requirements

Change-Id: I44f13a22528824a8b24ffb3b0e3075e870e5ee58
Merge "Add support for extension list"
Merge "Ignore most of the new hacking 0.9.2 rules"
Merge "Updated from global requirements"