Hi!

I'm continuing on my proposal to introduce a "document" element in
org-mode and the idea of seeing everything before the first headline
as the base level 0 outline for a file. I've attached two patches that
I'd like some public review of before pushing to master.

Patch 0001 introduces the document element into org-element.el, and
some restructuring related to that.

Patch 0002 makes it possible to use property drawers at the document
level. I've hopefully covered all related commands to make this work.
And I've added a bunch of tests to guard against future regressions.

Waiting for your comments!

Kind regards Gustav