- This was infinitely recursing because it was picking up fmt::to_string
(on macos) rather than formattable::to_string, which led to infinite
recursion and then a crash.
- Add a custom ghc::filesystem::path formatter (because it just seems
wrong to add a function into ghc::filesystem) instead of using the
to_string formatting. Same for boost formatting crap in simplewallet.
- Move the formatter structs into the `formattable` namespace so that
this sort of recursive error can't happen again.