VegBank

This is a feature request to allow vegbank users to create custom data
downloads. There was some work done on this a while back -- in the
StyleSheetGenerator class.

some progress on this has also been made, in that users can specify whether to
have empty values (,,) or null written (,null,). This bug is more about
choosing which fields, and we are far from that, given our current download method.

Pass params from user (web) which are used as hash keys to get potentially complex SQL attribute
selections. Then swap that big string into SELECT {0} FROM ...

Original Bugzilla ID was 881