Fix docstring for _Namespace._get_cli_value

Change-Id: Idea5f7c57c5e35f6de74bc7f2caac0ea6db35f35
Add section titles and fix markup of docstring

Add section titles to the module docstring for cfg.py so
http://docs.openstack.org/developer/oslo.config/cfg.html is broken up
and easier to scan quickly.

Fix a couple of minor markup issues at the same time.

Change-Id: I03df6842b29e62de1b3c923218f174cf65fdefdb
Fix test_version on Python 3.4

Since Python 3.4, argparse has been printing the version on stdout rather than
on stderr as it used to. We should fix this now because:
- this is an issue when packaging oslo-config in Debian Sid, which uses Python
  3.4;
- it will be needed when Openstack switches to 3.4 anyway.

Change-Id: I6a84009acb8621d62465c4cd2573200a07b6b4ab
Updated from global requirements

Change-Id: I2c06261c3a58ef711808a04b1639f6736c55b635
Graduate config fixture

Adds the config fixture from incubator and the associated tests,
updating both as appropriate for the new location.

bp graduate-config-fixture

Change-Id: I5a748c3b92b26c23101a565b7ca6790b8d00ec76
Reject option names prefixed with '_'

Such names are used for _Namespace's internal purposes.

Change-Id: I08c24f05ec3ef626b253ca3682439c1a162959e5
Related-Bug: #1284969
Merge "Reject option names prefixed with '_'"
Merge "Fix docstring for _Namespace._get_cli_value"
Merge "Add section titles and fix markup of docstring"
Merge "Updated from global requirements"