See issue/7fb03f234030b91c38cc4f5b48bd30cf5fd6a1de.

• move args to its own module

cleanup ABOUT definition

Squash review.

Rebased and restrict arg visibility to pub(super).

Rebase

Changes:

• Rebase
• Simplify error message and test value parsing

• Bring back the verbose parse error that carries its sources around
• Bring back impl FromStr, drop the separate parser function
• Use shiny new example IDs
• Move unit tests to the args module
• Use example IDs in unit tests

• Squash in review commits
• Rebase