Move to Solr UnifiedHighlighter

"You are encouraged to try out the UnifiedHighlighter by setting hl.method=unified and report feedback. It might become the default in 7.0. It's more efficient/faster than the other highlighters, especially compared to the original Highlighter. That said, some options aren't supported yet. It will get more features in time, especially with your input. See HighlightParams.java for a listing of highlight parameters annotated with which highlighters use them. hl.useFastVectorHighlighter is now considered deprecated in lieu of hl.method=fastVector. "