document global kwarg

eg. the 'lable' keyword

Would it be possible to add a field label, to the meta dict of the history, that defaults to the func field, but can be altered by an additional keyword argument that can be passed to the flagging function when called?

The purpose would be, to have a field that could be evaluated by plot, so that the legends in the plots would not have this nonsense/cryptic names. For example, it is predictable, that people will ask, "but what exactly is flagManual" (flag Handbuch?)?, "Why is there 2 times "flagRange" listed in the legend? "What does flagGeneric mean? and so on.

Since we have the possibility to generate history sensitive plots - (wich is quite a cool and handy feature, i can report from using it) - it would be just great to have the possibillity to fill it with meaningfull names...

I already got this questions in the context of generating the examples/use_cases: What is flagManual here?