Add a simple extension hook

This enables stand-alone modules to hook in to the command-line
handler in a dedicated API namespace.  These extensions have access
to the existing clients via the client manager but no way to add
another client to the manager is provided..

blueprint client-extensions

Change-Id: I4b2eaa780d8ba881db23d950d09b8702e9e314ef
Add metadata support for volume

Now able to pass metadata to the create method,
as well as update it with set, and remove it with unset.
I'm currently passing it as an optional param like the following:
--meta-data=key1=value1
which seems weird, what about
--meta-data=key1:value1
I'd have to update type too if that is the case.

Change-Id: I0fc8398768da015c1f53c5c564c68a2cfb53e778
Add policy to identity v3

use file for data blobs
add create/set/delete/show/list policy for v3

Change-Id: I5f68ef89dfb2241ea1aca00736ee6df5f6f03a9b
Merge "Add a simple extension hook"
Merge "Add policy to identity v3"
Merge "Add metadata support for volume"