removed tick lists and variable tick times
removed tick lists and variable tick times

handling tick events in simulation loop: moving towards fully event based (as opposed to tick based)

arurke/contiki,arurke/contiki,MohamedSeliem/contiki,MohamedSeliem/contiki,bluerover/6lbr,MohamedSeliem/contiki,arurke/contiki,MohamedSeliem/contiki,arurke/contiki,arurke/contiki,MohamedSeliem/contiki,bluerover/6lbr,bluerover/6lbr,bluerover/6lbr,arurke/contiki,bluerover/6lbr,MohamedSeliem/contiki,bluerover/6lbr,MohamedSeliem/contiki,bluerover/6lbr,arurke/contiki