Draft namespace

The purpose of the Draft namespace will be to support Wikipedia article creation without requiring users to publish in the main content namespace immediately (it will have no impact on whether user namespace subpages may be used for the same purpose). See also 57315. English Wikipedia requested this namespace (57569), so it will probably be the first Wikimedia project to have the new namespace.

Minimum requirements

 * User experience
 * 1) Page titles are pre-pended with "Draft:" or the localized equivalent in your language.
 * 2) There is an accompanying "Draft talk:" page for each Draft page, to facilitate discussion.
 * 3) Any user, anonymous or registered, will be able to create drafts.
 * 4) Any user, anonymous or registered, will be able to search for drafts. However, drafts will not be shown in the default search results, so users will have to choose to include them in their search filters.
 * 5) For now, only autoconfirmed users will be able to publish drafts, by moving them in to the main content namespace. This abides by the default requirement that users moving pages be autoconfirmed.
 * 6) TBD: how should categories behave on drafts? Theoretically, we can let editors use normal category syntax to categorize drafts, but suppress them from showing in the category listings. This avoids showing drafts in main content categories, while avoiding confusion and extra work policing the use of categories in drafts.


 * Technical requirements
 * 1) The namespace will, for now, be defined in wmf-config. Even if special publication behavior goes in core later, we will probably have to provide a way to specify which namespaces it affects, so using a site admin namespace rather than a core namespace is probably okay (we could still add an optional core namespace, later).
 * 2) Required behavior (e.g. hooks) will be implemented in an extension or wmf-config initially. If the latter, could be moved to an extension easily later.
 * 3) The namespace will have a robots policy that includes the following: it will be NOINDEX, to hide it from search engines, and NOFOLLOW, since regular pages are too, and scrutiny for spam may not be as high for drafts. (This also means disabling the associated magic words that can enable indexing etc., using wgExemptFromUserRobotsControl)
 * 4) Should not be a content namespace.  Such pages show up as content in Special:Statistics.  To count there, it should be moved to the main namespace first.

After the above is implemented, it will be tested on at least Beta Labs to confirm that behavior, before deploying to the first production wiki (probably English Wikipedia).