Torus model revision: adding bubble flow control for deadlock prevention and updated congestion control

Changing the hash function to bj_hash_little2, more additions to the MPI Sim layer operation matching

NOTE: caused an event size bump - you may need to update config files

Updated congestion control in dragonfly: now messages are saved in a waiting list at the routers in case of buffer overflows

so people can bring their own workload

- only activated if Darshan enabled at configure time
- currently fails with assertion

this will be used so that LPs can communicate with each other in a more
flexible way without having to pass around strings (notably, the next step will
be for the map context API to take advantage of this)

Adding group level mapping in the dragonfly: multiple routers can now be specified in the config file