Reinstate the hiding of events by event type across
all dives in the log. This was unintentionally removed in #3948.
Also change the event type to be specific to name and severity, and fix
bug causing 'Unhide all events' to not show when only individual events
were hidden.
This still leaves the inconsistency that hiding of similar events is
persisted across the switch between dives, but hiding of individual
events is lost when switching dives, which is mildly confusing.
Follow-up to #4092.
Signed-off-by: Michael Keller <github@ike.ch>
1309064873