Bad excluder

A small function that overrides values in dataseries with nan, if those values are flagged bad-ish. The func is thought to be used inside test funcs only - since this is a common task to do there and some ugly lines can get wrapped away. However - when including the small func in the testfuncs, i realized that the way how bad flagged values are handled in the testfuncs is inconsistent. some exclude them - some dont. I inserted the exclusion of bad flagged values where ever i thought it makes sence. But thinking aout that is confusing quite soon. I think we will need an issue about that theme to develop a general policy towards BAD flagged values in tests. (in general its the old annoying question of how to deal with test judgements made upon BAD flagged value insertion)