merge graph_matrix branch and fix conflicts.
add important annotation.reminds that the buffer length defines the playout delay and hence if a chunk can be offered.
combine graph files, matrix eigenvectors and simulation
This commit bind together SSSim with the matrix module which can load from file ".edges".the centrality properties of the peers can be derived from the matrix to speed up the distribution
add event driven simulation module
the '-e' parameter can be used to make SSSim use the event driven simulation approach