Fix typo

reported in https://github.com/elasticsearch/docs/issues/3
Use FHV's phraseLimit

This prevents poisoning the FVH with documents that contain TONS of matches
which take tons of memory and time to highlight.

Closes #4645
Stop FVH from throwing away some query boosts

The FVH was throwing away some boosts on queries stopping a number of
ways to boost phrase matches to the top of the list of fragments from
working.

The plain highlighter also doesn't work for this but that is because it
doesn't support the concept of the same term having a different score at
different positions.

Also update documentation claiming that FHV is nicer for weighing terms
found by query combinations.

Closes #4351
Fix compilation under javac 1.6.