add necessary fields to "document" item type

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To make "document" item type usable, the following fields need to be added/changed:

1. add "place" - to enter place of creation/publication

2. add "type" - to enter the type of document

3. add "cite as published/unpublished" toggle field - to note whether the document is published or not.

4. change "publisher" to "publisher/institution" - to denote that users can enter the name of the institution where, say, a working paper was drafted (but not published), for example:

1. Clark, “Should the IMF Become More Adaptive?” Working Paper WP/96/11 (Washington, DC: International Monetary Fund, 1996).

​http://www.chicagomanualofstyle.org/ch17/ch17_sec355.html

5. In cite.js/CSL, add a variable for published/unpublished; set fallback type as "book" if published, "article" if unpublished.

Alternatively, you can split "document" into "published document" and "unpublished document" (the latter could replace "manuscript" item type). This could make the interface less confusing for the user and will make it easier to format CSL.