wiki: indicate draft by filename

[cooper]

Currently you can indicate a page is a draft with:

@page.draft;

but this only works for quiki markup files. We need a more generic solution that can be used for any filetype, like Markdown.

Either to replace or in addition to the @page.draft flag, we should support the .draft file extension - for example, page_name.page.draft or page_name.md.draft.

• the primary extension is still needed to determine it is a page file
• page scanning functions would include it still, so they will be updated to look for .*.draft files
• the wiki/webserver will refuse to publicly serve it (same as with @page.draft), EXCEPT for previews etc which use DisplayPageDraft()
• wiki/revision should have a method to change the draft status, which renames the file
• adminifier would provide a graphical way to change the draft status, leveraging that method

[cooper]

in adminifier, you should also be able to create a draft from an existing page. then when publishing it, overwrite the original page. maybe it could be a setting whether to create a draft by default.