Add version list command

Lists version of installed python modules

Change-Id: I76a51d3d6783f46ef2daa0a41626019a880a2a50
New extension support

Define extension interface to include setting API versions and global
parser options

This exposed some issues in the object api tests that needed to be cleaned up

Change-Id: Ic9662edf34c5dd130a2f1a69d2454adefc1f8a95
Merge branch 'version-list' into dt-test
Merge branch 'image-v2-v2' into dt-test
Merge branch 'identity-ec2-tests' into dt-test