Structure of AdFlow

The simulation is divided to dissemination rounds.
Some of the nodes in the P2P overlay are advertiser nodes with some target audience.
Each round, each advertiser node generates new advertisement for the target audience.
The advertiser nodes then use the DistributionManager class to select seeding peers - the
peers that will begin the dissemination.
Each peer uses the DisseminationManager to decide whether to forward the ad to the neighbor.
Churn is simulated with round granularity - node are up or down throughout a whole round.
Up times are distributed using weibull distibution implemented in the Churner class.
After the dissemination, impression of the advertisements are simulated.
at the end of the round, each node sends impression notices to the corresponding advertiser nodes.
Advertiser nodes reply with payment notices, so that the nodes could use that information for the dissemination of the advertisement during the next round.
Different payment models are implemented.