more than one field and even more than one index should be the source of the dictionary
declaring which field is part of a dictionary should be declarative @AddToDictionary(name="main-dictionary")
(with probably an optional field name(s))
for a given dictionary name, we need to associate an index and probably a field prefix (to share the same index
for all dictionaries). This couold be by annotations or in the configuration (not sure)
this index should be kept like any other DirectoryProvider in the HSearch intrastructure (we could then reuse
ReaderProvider internally and don't have leaks).
we will probably add a manual dictionary reindex method and the SpellChecker API should be in the SearchFactory.
sf.getDictionary("main-dictionary").spellcheck(word, suggestion, entity, properties...); //not sure how useful is this one really
this needs to be refined.