Adding stemming functionality and reorganize package tree

* How did I ?
- Use hunspell implementation of stemmer (hunspell.jar and jna-4.0.0.jar
  required). Stemmer interface expose only one method: stem(), which get
  String (word) and returns list of String's (words).
- Create packages: analysis.hunspellJNA and analysis.jazzy instead of
  spellChecker.hunspellJNA, spellChecker.jazzyJNA.

* Note
HunspellStemmer and HunspellSpellChecker use the same dictionary.
These implementation are independant and both have its own copy of
dictionary. Implement something like HunspellAnalyzator or HunspellFacade
which allow for common dictionary in both classes can be a good idea.