Change the "silent" handling code to be "verbose" handling. The devault is

Change the "silent" handling code to be "verbose" handling.  The devault is
still to print each item as it happens, but now there are more options.

- you can use letters 's' or 'q' to be silent/quiet
- you can use letter 'v' to be verbose (default, print each item)
- you can use positive numbers to show each Nth item (default = 1, like 'v')
- you can use negative numbers to show output every -N seconds

The "--threads" command now takes a mandatory "verbose" flag because with
large numbers of threads it is too much output.  Note that this flag only
applies to the spawning of the threads and not the individual commands
(which can have their verbosity specified separately).

Example:

          device number-v v-command    v------v-command args
obdctl --threads 100 20 2 test_getattr 10000 -5
    threads count-^   ^-threads verbosity     ^-test_getattr verbosity

- run 100 threads, and print status for each 20th thread started
- on device 2 run test_getattr for 10000 attrs and print status once per 5sec