crux exploration

[matt-beanland]

as an exercise what would this yarn look like if IEEE1164 spoke the language of logic rather than relations?

[matt-beanland]

found a bug in crux and submitted a PR. Was to do with exactly_one falsely indicating true with >2 terms, where more than 1 was true. ash-project/crux#27 and PR ash-project/crux#26