Added multithreading to language lookup.
persistence for already computed decisions whether a word is German
Merge branch 'word_language_persistence' of https://github.com/neradis/index-vivus into word_language_persistence
Merge branch 'word_language_persistence' of https://github.com/neradis/index-vivus into word_language_persistence
Changed Language enum to services.Language
check for null-value to avoid NullPointerException
Added batch lookup