Hi,

This patch introduces a document level property drawer. 

This has been discussed previously in a larger context:
- https://lists.gnu.org/archive/html/emacs-orgmode/2019-06/msg00000.html
- https://lists.gnu.org/archive/html/emacs-orgmode/2019-08/msg00339.html 
- https://lists.gnu.org/archive/html/emacs-orgmode/2019-09/msg00010.html

The patch is a somewhat modified version of what was included in the third 
link above.

The following will be true for document level property drawers:
1) In the same way that one can have a property drawer for a heading, one
   can have a property drawer for a whole document.
2) All existing commands that can work with property drawers will
   (shall) work also on property drawers before the first heading.
3) Properties defined in a property drawer will have precedence over
   properties defined as a property keyword, if the same property is
   defined using both conventions.
4) The position for the document level property drawer is:
   - At the first line in a file that is not a comment or a keyword.

     I.e. the following will work:
     #+begin_src org
       # -*- mode: org -*-
       ,#+TITLE: Test
       :PROPERTIES:
       :CATEGORY: Test
       :END:

       Preamble 

       ,* Some heading
       Some content
     #+end_src

     but not this:
     #+begin_src org
       Some comment and/or empty line

       :PROPERTIES:
       :CATEGORY: Test
       :END:

       ,* Some heading
       Some content
     #+end_src

What do you say?

Regards
Gustav Wikström