Renamed readable_format flag to human

Closes #3541
when doing range queries within a query_string query, the range terms should only be lowercased if the field is not numeric

fixes #3540
Share shards computation logic between searchShards and searchShardsCount
Prevent FVH from entering a very long running loop on large docs with high freq phrase terms.

Terminate phrase searches early if max phrase window is exceeded in
FastVectorHighlighter to prevent very long running phrase
extraction if phrase terms are high frequent. See LUCENE-5182

Closes #3543
Bound processor size based cals to 32
We use number of processors to choose default thread pool sizes, and number of workers in networking (for HTTP and transport). Bound it to max at 32 by default as a safety measure to create too many threads.

This relates to #3478, where we set the default to 24, but 32 is probably a better default.

closes #3545
Smarter default to `index.index_concurrency`
closes #3546