#42 improve document management

[John Bywater]

People have said it is time consuming to put documents
and files on the website, and 'break them down into
their constituent parts'. (Need to clarify what this
means with user.)

[John Bywater]

Logged In: YES
user_id=133756

do things like:
1. only list those documents that are not already linked in
document elements filename selection (assume each doc is
linked once only) 2. present all documents in a list on
admin page 3. feedback about what happened to an uploaded
document on admin page 4. list document elements which don't
point to a real document anymore on admin page 5. list
documents which aren't referenced by any element