Get dst/src from MPI Calls

[cwschilly]

.cali files are structured like:

    ...
    {
        "event.begin#mpi.function": "MPI_Send",
        "mpi.rank": 0,
        "time.duration.ns": 167010,
        "time.offset.ns": 240363845
    },
    {
        "mpi.comm": "2",
        "mpi.comm.is_world": "true",
        "mpi.comm.size": "4",
        "mpi.msg.dst": 2,
        "mpi.msg.size": 4,
        "mpi.msg.tag": 1,
        "mpi.rank": 0,
        "mpi.send.count": 1,
        "path": "MPI_Send",
        "time.duration.ns": 47307,
        "time.offset.ns": 240411152
    },
    {
        "event.end#mpi.function": "MPI_Send",
        "mpi.rank": 0,
        "path": "MPI_Send",
        "region.count": 1,
        "time.duration.ns": 5813,
        "time.offset.ns": 240416965
    },
    ...

The cali2events.py script successfully pairs any event.begin records with their corresponding event.end.

However, for MPI Point-To-Point calls, more information is included in the "in-between" record (see above).

Find a way to get this data (src, dst, size) into events.json so that we can track calls in the visualizations.