Make custom formatting better

[mendelsshop]

In #37, I Implemented custom formatting using format_enter/format_exit.
I defaulted to using Display for formatting, like format! and friends.
Sometimes something does not implement Display so with format! you can do :?.
This PR allows format_enter/format_exit to do that and more (whatever other custom formatting options are supported by format).

[mendelsshop]

One idea that I had, was right now the way I am doing it is mostly manually parsing the format string.
Instead, if we see format_enter/format_exit, we basically just pass the format string directly to println!/log::trace!, and let them do all the parsing format string work.