Expand support for command extensions

Allows client libraries to have complete access to the rest of the
OSC ClientManager.  In addition, extension libraries can define
global options (for API version options/env vars) and define
versioned API entry points similar to the in-repo commands.

The changes to ClientManager exposed some issues in the existing
object api tests that needed to be cleaned up.

Change-Id: Ic9662edf34c5dd130a2f1a69d2454adefc1f8a95
Restore Object API name 'object-store'

It's used in the service catalog, doh!

Change-Id: If8f6db49c84756fd8e58cc68910160da4cd99b5d
Add return Closes-Bug: 1246356

Change-Id: I70999a91062b9c61e5f420b1ed33a45086b62fd4
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
Add missing requests and six requirements

From global-requirements: requests>=1.1, six>=1.4.1

Change-Id: I536adc511931229a268ba81f81aef1aed59b33eb
Merge "Add missing requests and six requirements"
Update docs for plugins and release notes

* Fill out the existing command and man page
* Add a plugins page.
* Begin the release notes for 0.3.0

Change-Id: I4527fed28a10a9d79fc8f6c1d925a4bf0d0a7a36
Merge "Add module list command"
Merge "Update docs for plugins and release notes"
Merge "Bring RESTApi closer to ithe imminent keystoneclient.Session"
Updated from global requirements

Change-Id: I065a67d560efca0907da9fcaa8d5ce4712dfa2c1
Remove mox3 requirement

mox3 is only used got py3 testing when converting tests from mox,
all OSC tests are new so we don't need it.

Change-Id: I2fae539e99143f91048c95d1e46cfbd7b0e9bdb0
Release notes for 0.3.0 release

Change-Id: I6f025b745378613eb674e13dd503e57d049a3e50