Relaxed option naming

[phlptp]

If merged this pull request will relax the restrictions on option naming and subcommand naming.

Allowing inclusion of all characters except
starting with:

• - since we need to recognize - and -- as different options and -- has some special meaning
• \n since that would cause all sorts of chaos with the formatters and other things
• ! used as a special character for setting default values
• allowing this would create the potential for difficult to debug user entry errors for example "-- input, input" would be adding an extra space accidentally, But if space were allowed this would read fine as a single almost impossible to use option.

and anywhere in the option

• \n same as above
• =, and : they are fine as a first character but after that they are used as a value separator so can't be allowed in an option
• { {} is used to indicate default values
• allowing this would create the potential for difficult to debug user entry errors for example "--input input" would be forgetting a comma to separate an option from the positional. But if space were allowed this would read fine as a single almost impossible to use option.

this will address #580
also allow lots of amusing things like --:) as an option

A couple questions in #592 we talked about adding a check on group_names and a few other things. particularly in regard to newlines. I need to do that yet.

But in regard to subcommands through the add_subcommand I am inclined to leave the check for spaces in the subcommand name in place. The reason has to do with error catching. Most subcommand names don't have spaces but their description does quite frequently. Meaning the check on spaces catches some potential errors in the API call. Removing this restriction would likely cause additional errors that might be hard for a user to spot initially.

Then the question is should we allow newlines in App names? If not might be worth adding an additional validator to catch that and use it for app names, aliases, and group names.

[phlptp]

TODO

• readme updates
• additional test cases for subcommands
• validators for group names, app name, aliases
• book updates

[phlptp]

Added a validator for group_names, aliases, and option group names. But not app names. App names can still have new lines, so it is possible to get a subcommand with a new line but not easy. Should we restrict this as well?