Mark services as Beta to indicate that the interfaces may not be stable

[Everett Toews]

As we commit all code to master (which is fine), it's easy to wind up releasing code that isn't completely stable. The interfaces and behaviour may change when using a particular service.

We need a way to mark services as Beta to indicate that the interfaces/behaviour may not be stable for our users. That way if they choose to use code that may not be completely stable yet, at least they be forewarned.

[Brian Curtin (brian.curtin)]

In the Python standard library, there's the idea of provisional libraries, such as asyncio. https://docs.python.org/3/library/asyncio.html includes a note at the top saying it might change. We should probably just do the same.

[Everett Toews (everett-toews)]

Based on the IRC discussion [1]

For every resource of a beta service, include at the top of the class docstring "BETA: This API is a work in progress and is subject to change."
For the Proxy class of a beta service, include at the top of the class docstring "BETA: This API is a work in progress and is subject to change."
For the proxy and user guide documentation of a beta service, include at the top of the doc

    .. caution::
       BETA: This API is a work in progress and is subject to change.

[1] http://eavesdrop.openstack.org/meetings/python_openstacksdk/2015/python_openstacksdk.2015-12-08-19.00.log.html#l-45

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/255465

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/255465
Committed: https://git.openstack.org/cgit/openstack/python-openstacksdk/commit/?id=355945c7f50821584455f594f9924f94b5455447
Submitter: Jenkins
Branch: master

commit 355945c7f50821584455f594f9924f94b5455447
Author: Terry Howe <email address hidden>
Date: Wed Dec 9 13:08:48 2015 -0700

    Add admonition to telemetry code

    This code is subject to change in the near future. The alarm
    class is probably moving out of here and many of the resource
    property have aliases. We have agreed not to support the old
    aliases going forward, because it doesn't work well. The
    admonition can be pulled after these issues are fixed.

    Closes-Bug: #1468086
    Change-Id: Ica464a6c1e2281f4acbd25a121a399b6b0c81376