Major changes made to failures methods. Re-written node removal method
which checks routes, now no errors from this part of the simulation from
the limited testing done on this. Also changed the way in which nodes are
selected to be removed with a failed_junctions list. These changes have
again removed all errors from this aspect of the code.
Need to look at the edge methods still,visualising edge failures in a geo
failure and sorting the weighted shortest path method when rerouting flows
where the weight is hard coded in curently.