doc updates to match "help" better

This makes the documentation a closer match to "help" output:

 - "pathmove" somehow was not documented in the User's Guide

 - "jtag_nsrst_assert_width" and "jtag_ntrst_assert_width"
   are new; both needed descriptions.

 - Removed two undocumented and fairly useless script mechanisms:
    * production/production_info/production_test ... using it,
      requires replacing everything; so having it adds no value.
    * cpu ... way out of date; hopeless to keep that current

Note that anyone using that "production" stuff already defines
their own procedures, and can keep using them with no change.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>