[rtags] Enhance repr of rtags * we don't care of the class, the registry id is enough (never seen a case of sub-classing) * add the module from which the rtag is coming as well as parent rtag if any.

version=3
opts=uversionmangle=s/(rc|a|b|c)/~$1/ \
https://pypi.debian.net/cubicweb/cubicweb-(.+)\.(?:zip|tgz|tbz|txz|(?:tar\.(?:gz|bz2|xz)))