Improvements and fixes for performance of PUSH/PULL in local_thr and remote_thr.

- option to set number of zmq threads on the command line for local_thr
- option to set number of zmq_threads and workers in remote_thr
- option to set SND/RCV buffer sizes on command line
- option to set whether to PUSH/PULL on command line
- option to set to use zmq_recv or zmq_msg for transfer on command line
- better timing function
- corrected and improved throughput reporting
- HWM and DELAY socket options
Merge pull request #523 from ambitslix/perf

Improvements and fixes for performance of PUSH/PULL in local_thr and rem...