#20 Allow displayed fields specified by URL

[Eric Vaandering]

We can now specify for events, topics, etc. which
fields are shown, how many rows & columns a field
spans, etc.

It would make sense to also be able to specify this in
a URL so that users can craft their own "reports" as
links from web pages.

E.g.,
ListBy?topicid=12&fields=author,topics,abstract_1_3_2_1
would list documents with a topic and would show the
authors, topics, and abstract. The abstract would span
2 rows.