0.15.1: zip / tar.gz / issues

Release Notes:

Twitter river: “user.screen_name” should not be analyzed (#715)
Add http and transport simplified host settings (#706)
Clear Cache API: Add specific cache clear for id, filter, field_data, bloom (#716)
Improve from hits pagination (duplicates) (#717)
Index Filter Cache: Add resident type, and max_size to soft/weak types (#721)
Mapping: When _all is disabled, optimize to not gather all entries (#722)
Zen Discovery: Rename `discovery.zen.initial_ping_timeout` to `discovery.zen.ping_timeout` (still support the old setting) (#723)
Bulk API: Improve memory usage when executing large bulk requests (724)
Peer Recovery: Batch translog based operation recovery based on size and not just number of operations (#729)

Handle cluster join request on a non IO thread (#702)
River not recovered when using single node after shutdown (#711)
Single node cluster comes up as red with local gateway (#714)
Acknowledge problem for put mapping with multiple indices or all indices (#720)
Percolate: Failure to percolate with specific query (when creating the _percolate index before the actual index) (#725)
Ids with # in them will cause search failures, also, fail when # is used in a type name (#728)