Back to shared implementation method for .option and .requiredOption

[shadowspawn]

Pull Request

Problem

Implementing .requiredOption() using .option() was very compact, but having second thoughts. Some drawbacks mainly for subclassing:

• tricky to modify option creation with chain of methods being called
• fragile reliance on new option being last in options array
• calling .addOption without final configuration in the passed option

(Prompted by thinking about how to add an override to add a matching --no option for every boolean option.)

Solution

Just shift the shared code back into ._optionEx like previous pattern, but with the new code.

Much as @abetomo suggested in #1331 (comment) !

[abetomo]

LGTM.
Thanks!