A silent collector says so, and the catalog says when it was really confirmed

The fleet list said 'active' for a collector that had not checked in for forty hours; the lifecycle state was true and the reading was not. elixir_collectors and the fleet page now say what a collector is doing: active when it checked in within the hour, silent when it is enrolled to run and has not (with when it went quiet and when it was last seen), draining when it was stopped on purpose; the enrolment state stays beside it as lifecycle. The maintainer is told once each time a collector goes silent, the way quarantine already told him. Also fixed: the card catalog's fetched_at said 09-10 while the catalog had been fetched and confirmed every night since; it now reads the poll's own admission stamp. Contract 6.1.0, additive.