add per-link events.
Add a new flag (-E) to turn on the per-link event. This implies the event-driven mode (-e).Each peer i sends an offer to its neighbor j every offer_interval times probability of j seconds, deterministically.
refactor action event initialization and standardize event priority
two default priority levels are defined: HIGH_EVENT_PRIORITY and LOW_EVENT_PRIORITY
add copyright banner to "event driven" files
add event driven simulation module
the '-e' parameter can be used to make SSSim use the event driven simulation approach