changed rule name macros
fixed the errata
another fix for errata
Merge pull request #725 from EgbertRijke/rulenames

changed rule name macros
introduced macro for uniq
renamed the uniqueness principles of products, unit and named the uniqueness principle of dependent pair types
Merge branch 'uniqueness' of https://github.com/EgbertRijke/book into uniqueness
included \uniq in list of symbols