[templates] add bash template and style guide

[budRich]

Rules of bash:

All scripts should at least have long and short options for help and version.
Help always contains Short and long description, synopsis, options descriptions.

Environment variables are always ALL_CAPS.
global variables and arrays are prefixed with __two_underscores
all other variables are declared local.
functions are all lowercase(){ : ;}

informative mandatory globals always at the top of the scripts after shebang (#!/bin/env bash)

three mandatory functions: main() and init() printinfo()

special optional global variables are __lastarg and __stdin. __lastarg is defined after options are parsed, __stdin` is defined before entering main function.

maybe add mandatory function deticated for option parsing.

options are defined like this:

__optargs[longoption]=ARGNAME
__opttext[longoption]=description
__options[longoption]= followed by optional shortoption, colons, and +.
one colon means that the option have a mandatory argument, two colons are optional argument, + will automaticly add the argument to a global variable named __LONGOPTION, if no argument is given set the variable to 1.