count skipped data

## Reasons
- Skipped BWS sets are an indicator that all item are similar (according to some user-specific decision criteria)

## Problem (wontfix)
- Information about skipped BWS sets are not in the scope of this package because it is too specific to UI programming. 

## TODO
- [ ] function to filter (i.e. a simple pythonic loop) evaluated BWS sets with a skipped message