Add stemming (Porter algorithm?) to LuceneTagger

[stargazer33]

Having stemming in Java code we will have less redundancy in queries than at the moment.

Phrases like this:
"Backend Developer"~1 OR "Backend Development"~1
will be just "Backend Developer"~1
and stemming algorithm will cover all the variants

See config.java-backend.yml, under "lucenetagger" and "query"