create asgsh "style guide" for contributed commands, sub commands

[wwlwpd]

A short document would suffice for describing how to add tools to the asgsh environment. The idea would be:

• user creates handy scripts for their activities (could be for "real time", development, research, or hindcasting, etc activities)
• user ensures script(s) follow UX (commandline arguments, things asgsh may need to "register it")
• user "registers" tool with asgsh - basicaly this would enable: installing script when asgs environment is built or shell is updated, asgsh's help can report some useful information about this command, provided tool "plays nice" with other asgsh tools and built-ins
• it'd be preferrable that the tool is a "script" but if it or things it might use must be compiled, then it'd need to somehow be able to tell asgs-brew.pl that there is a build process associated with it