add chapter "ownCloud Bug Triaging"

@carlaschroder lots to do still - I'd like feedback especially from Jennifer, but also @dragotin @karlitschek @danimo @LukasReschke @PVince81 and others ;-)

Mostly on the gaps and the questions in there...
Da gibts was von Ratiopharm: https://github.com/owncloud/core/wiki/Maintainers