json commands should begin, not end with json.

This makes them all group together into one place in the cooand-line help.
add 'hidden' command parameter

Actually, this implements ^D and quit as synonyms for the "exit"
command.  Unfortunately, this requiresd the ocean to be boiled :-(
don't dump stack trace on user error.
Add h as synonym for 'help'
no C++ stack traces on warning; only on error

Its goofy to print stack traces for warnings.
Merge pull request #188 from linas/web

assorted minor cleanups