Implement class AveragerPairWeighted

[Peter]

Functions should fulfill the following: 1) all weights equal to unity yiels same as Averager 2) Rescaling all weights yields no difference 3) adding a data point with weight zero yields no difference 4) Additivity add(w)+add(w)=add(2w).

These conditions should be tested in test program. Peter realized that all conditions can not be met, so some thinking must be done (skip either 2 or 4).

[Peter]

Class fulfilling: 1) all weights equal to unity yiels same as Averager 2) Rescaling all weights yields no difference 3) adding a data point with weight zero yields no difference

[wwwrun]

Milestone weighted statistics deleted