make before break!

createOffer:
    create new ice gatherer, icetransport, dtlstransport, store as new[...]
    wait for new dtlstransport to be established
    dispose old things

setRemoteDescription:
    detect ice restart as change of ufrag/pwd 
    create new ice gatherer, icetransport, dtlstransport, store as new[...]
    wait for new dtlstransport to be established
    dispose old things
    -- do this first as it is testable with chrome (requires interop test)