make __repr__ more nice and include in __all__
Change-Id: Iecfe6326f2d35a2210c03f7bd8c84dc2830b19ea
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/23120
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Enrico Faulhaber <enrico.faulhaber@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>