CYKLO-927 Add TestNg
CYKLO-927 Create test for StemFilter. Data is ready, but no test yet. WIP
CYKLO-927 Check is stem filter creates stems and inserts them into stream correctly.
CYKLO-927 Add test which adds document to index and then validates that stems and original words are available.
CYKLO-927 Add fest assertions
CYKLO-927 Commit changes as they are in StemFilter. WIP