`unveil<>` renamed to `fmt_unveil<>`, now packs args to u64 imitating va_args
`bijective...` removed, `cfg::enum_entry` now uses formatting system
`fmt_class_string<>` added, providing type-specific "%s" handler function
Added `fmt::append`, removed `fmt::narrow` (too obscure)
Utilities/cfmt.h: C-style format template function (WIP)
Minor formatting fixes and cleanup
