refactor: separate out storage of parsed option in results

[shadowspawn]

Move the code for storing parsed option to its own routine:

• simplify changes to conventions under discussion (e.g. Unnecessary arrays in result values? #19)
• simplify reuse of logic when add short options
• reduce duplicated code

The intent is zero changes in functionality, zero bugs fixes, zero changes to conventions.

[bcoe]

This seems like a good refactor, is your thinking that we could then easily move to a Map as suggested in #32?

[shadowspawn]

Yes, refactor simplifies all of:

• finish move to xor flags/value
• drop unnecessary arrays in results
• switch from object to Map for internal logic
• add support for short flags