752 - Formatters are now simple functions

752 - Formatters are now simple functions
onlyShowUnchanged param and dependency fixing
si -> siSuffix
Removing onlyShowUnchanged var from siSuffix
Fixing API breakage in quicktests for formatter

Close #752.
rather than typing formatter `any`, let's define a formatter interface for functions of type `(any) -> string` and use that?