Stop filtering out events with beginning or end flags

This made sense briefly when libdivecomputer reported ceiling data through
events with those flags, but it actually made us hide valid events from
some divecomputers that give us only very limited information (e.g., deco
events from some Suunto divecomputers).

Reported-by: Henrik Brautaset Aronsen <subsurface@henrik.synth.no>
Analyzed-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>