Version v0.2.0: with struct variants implemented

Release v0.1.4: support of `xx=yy` in format patterns in `display(..)`

Version v0.1.3: better metadata support

Version v0.1.2: implement support for doc strings for variants

Version v0.1.1: fix of unqualified usage of std::error:Error in macros

Version v0.1.0: initial release, probably fully featured