libzypp: Filters and Functors

libzypp 17.38.8

Filters and Functors

## Topics
| Collection solvable filter functors.
| All functors should be able to process Solvable as well as PoolItem.
| Filter functors operating on ResObjects.
| A simple filter is a function or functor matching the signature:
| Functors for building compex queries.
| Some logical functors to build more complex queries:
| ACTIONFUNCTOR

## Detailed Description