[DOCS] Add /_search_shards documentation
Improved bloom filter hashing
Make improvements to how bloom filter hashing works based on guava 17 upcoming changes, see more here (https://code.google.com/p/guava-libraries/issues/detail?id=1119)
In order to do it, introduce a hashing enum, and use the (unused until now) hash type serialization to choose the correct hashing used based on serialized version.
Also, move to use our own optimized murmur hash for the new hashing logic.
Parse has_child query/filter after child type has been parsed

Fixes #5783
Fixes #5838
[SPEC] Renamed benchmark endpoints

benchmark.submit -> benchmark
benchmark.list   -> list_benchmarks
benchmark.abort  -> abort_benchmark

And fixed the related tests
[SPEC] Added missing list_benchmarks test
[SPEC] The scroll_id is no longer a required qs param
Can be passed in the body instead
[DOCS] getting started tutorial
[SPEC] Added path without scroll_id to clear_scroll
Change default merge throttling to 50MB / sec

The current setting of 20MB/sec seems to be too conservative given
the capabilities of modern hardware. Even on cloud infrastructure this
seems to be too lowish. A 50MB default should provide better out of the box
performance