Improve settings doc: add "added in <release>" information

[Julie Pichon]

We direct users to http://docs.openstack.org/developer/horizon/topics/settings.html when they have a question about settings. They also find the page when searching for help. However it's not clear at all what release a setting is available for, especially when it's added to a version that hasn't been released yet.

I think we should add information like "added in Grizzly" or "new in 2014.1 (Icehouse)", similar to what the Django or Python docs do. It is really useful.

https://docs.python.org/2.7/library/unittest.html#unittest.TestCase.setUpClass
https://docs.djangoproject.com/en/1.6/ref/settings/#csrf-cookie-httponly

See related bug 1221115, which is about adding missing settings (but we don't need to wait for it to be resolved to start fixing this one).

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/92877

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/93479

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/92877
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=83daca331a2198f5a2f25e2841e85c01d5caf08a
Submitter: Jenkins
Branch: master

commit 83daca331a2198f5a2f25e2841e85c01d5caf08a
Author: Gary W. Smith <email address hidden>
Date: Wed May 7 15:52:53 2014 -0700

    Add "new in" tags to docs for new Icehouse settings

    Also re-alphabetize settings list

    Change-Id: Ieb47e9f2a0be4906a744970a9d17dd5177e59fc0
    Partial-Bug: #1300710

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/93479
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=90a96dd057f18603a495410e9178e1417d8ff087
Submitter: Jenkins
Branch: master

commit 90a96dd057f18603a495410e9178e1417d8ff087
Author: Gary W. Smith <email address hidden>
Date: Mon May 12 16:08:05 2014 -0700

    Add "new in" tags for pre-Icehouse settings

    Change-Id: I7e1a3f5f20075638f14ddfb59456253e15704fdf
    Partial-Bug: #1300710

[Gary W. Smith (gary-w-smith)]

This bug should have a status of Fix Commited, since the last change really should have said Closes-Bug instead of Partial-Bug.