added topologies for 20mbit,30mbit,40mbit and 50mbit bottlenecks
added quality switches to calculate_average and playerlevelhistory
also made sure that calculate average can be run from
commandline again (without parameter)
updated simulation template script so we can run several simulations;
added cwnd parameter to congavoid and adapted all other files 
so the cwnd parameter is being passed to the respective downloaders