The codes-workload-test and codes-workload-mpi-replay both support
the new paramters of the bgp-io language workload generator. Also,
support has been added to the config file and codes-workload-mpi-replay
program for loading the parameters of a darshan config file.

Improve the performance of the darshan i/o workload by converting the
linked list of per-rank contexts to a hash table.

Update the output directory argument of the mpi-replay tool to just
specify an already existing directory to perform the workload I/O in.

Modify the mpi-replay tool (located at tests/workload) to spit out
verbose information on each event it replays, if user specifies
-v option. Also, modify the mpi-replay tool to perform no-ops for
each replayed event, if user specifies --noop option. The replay
tool should function properly for all workload types now.

TODO: The tool should offer functionality for initializing the context
of the output replay directory. That is, the tool should first scan
the given workload and create all files and preallocate space for all
I/O ops in the workload. Currently, the replay tool will fail on any
files that are not explicitly created by the workload.

adding the mpi-replay tool to the tests/workload directory for replaying workloads from the codes workload api