TagLL needs a public API to allow TagClusterReducer implementations

While implementing a TagClusterReducer that removes Tags that do not overlap proper-nouns I noticed that one can not have own TagClusterReducer implementations because TagLL (used by the Interface) is not a public class and does not define a public API.

This pull requests makes TagLL public and adds an public API sufficient for implementing TagClusterReducer.

Summary of changes:

* changed class from default to public
* added public getter for properties needed by TagClusterReducer implementations
* changed removeLL() method from default to public as TagClusterReducer need to be able to reduce tags