Functions used to manipulate tagged collections (development version)

 Tagged collections are collections of items tagged with multiple categories.
 libtagcoll provides general infrastructure to handle tagged collection data,
 plus various kind of tagged collection manipulation functions:
 .
  * apply various kinds of transformations to the collection;
  * generate and apply tag patches;
  * discover and show implicit hierarchical relationships between
    tags;
  * organize the collection in an intuitively navigable hierarchy.
  * keep an on-disk index of the tag data
 .
 Warning: the API has not yet been stabilized and is subject to change in
 future versions. This is why the library is distributed in a -dev package
 only.