minor optimisations in auras.lua

unset OnUpdate on buttons when timeLeft < 0
move mouseover force update below event relevance check
more auras.lua optimisations

add configChangedListener capability to modules
store mod.db.profile.{display,behav} when options are changed to reduce lookup
only fire UNIT_AURA on mouseover for certain events
reduce unnecessary locals in COMBAT_LOG_EVENT_UNFILTERED
remove more locals, more UNIT_AURA fire for the mouseover properly