Bring RESTApi closer to ithe imminent keystoneclient.Session

Prepare to use the (soon to be) common Session from keystoneclient
* Rework RESTApi to eventually be a subclass of keystoneclient.Session

Change-Id: I68e610f8b19a3f6267a93f7bf3de54a228be68aa
Update OSC's CommandManager subclass

cliff.commandmanager.CommandManager gained an option, update
openstackclient.common.commandmanager.ComamndManager to match.

Also add CommandManager.get_command_groups() to return a list of the
currently loaded command groups.  I expect this to be useful in
upcoming client diagnostic commands for plugins/extensions.

If these turn out to be generally useful we'll propose them to
upstream cliff.

Change-Id: Ic15a7ca0ef975ca679e753be861be7c628b8e10c
Add module list command

Lists versions of installed python modules

(Origianlly proposed as 'version list')

Change-Id: I76a51d3d6783f46ef2daa0a41626019a880a2a50
Merge branch 'restapi-v2' into dt-test
Merge branch 'module-list' into dt-test
Merge branch 'image-v2-v2' into dt-test
Merge branch 'identity-ec2-tests' into dt-test