remove call to forbidden api
remove slow methods
use IndexSearcher to gather term statistics.

But: how to get the index search from calling class? Also: How to make
DFS_QUERY_THEN_FETCH work correctly?
remove null checks from script, is not needed
split TermInfo ind statistics and iterators
rename getDocCount() -> docCount()
make flags available without the _terminfo prefix
document the new flag setting and remove the methods returning positions as array
remove todo, we can assume in order scoring
advance instead of nextDoc()
throw ES exception instead of RuntimeException
remove unused class
remove check for docs out of order
make fields private and remove unused field
rename _terminfo -> _shard
small things