fix adjust_priority_with_status option: save when we change this option and correctly get autopriority_* values

do not do utf-8 twice; make sure before_/after_time/name possible newlines are taken into account in history window too

introduce GajimGeneralException and use that instead of RunTimeError when raising so instances are not created. This is better because python can also raise RunTimeError, which we will catch by accident and we do not want that to happen

unite room and server name resulting in a room jid interface [so it aligns with add new contact]. fixes #2504