added facility to filter queries to assist with debugging
added function to escape debug output.
Fixes RandomFilter so that rng is reseeded from query. So now it should be more predictable since prior journal operations don't affect the filter.
Fixed issue in DeferredJournal with file numbering
MainDownloader can now download a single link
Some refactorying
Add back ability to specify seed in RandomFilter
Customisable timeout for DeferredFileJournal