added the '--help' option to every command
added pretty much all options that the commands currently support. still to be done: 'list'
started the user doc
included the list command into considerations. Improved install script
everything seems to work, basically.

The general setup of how commands can be executed works (calling 'sgcheck <command>', whereas <command> is a script located in $SG_SCRIPT_PATH (linux environment variable).

The commands seem to work correct, at least with standard options.

known bug:
	commands ignore about the '--help' option, which results the command being executed (instead of just printing a help file), if you type:
		'<command> --help'

ToDo:
	test everything with different options
	add support for the '--help' option for every command