Core: upgrade to current Lucene 5.0.0 snapshot

Elasticsearch no longer unlocks the Lucene index on startup (this was
dangerous, and could possibly lead to corruption).

Added the new serbian_normalization TokenFilter from Lucene.

NoLockFactory is no longer supported (index.store.fs.fs_lock = none),
and if you have a typo in your fs_lock you'll now hit a StoreException
instead of silently using NoLockFactory.

Closes #8588