Frontier reports extract: refactor filters and harmonize UI table columns

Currently filters logic is hard-coded in the FullFrontierReport class which is a bad design. This class should offer a set of iterators for filter classes to work with.
Additionally the UI tables for the frontier report extracts should all contain the same columns:
1) Queue name
2) Discovered URI count
3) URI to collect count
4) budget spent / total budget
5) last enqueued URI