Fixed NPE when using `has_parent` or `has_child` filter/query.

The NPE occurred when for an arbitrary segment no parent documents exist for a has_parent filter/query and no child documents exist for a has_child filter/query.

Closes #2297
return null instead of empty doc set
null can more easily be optimized in other filters
fix detection when JTS / spatial4j are not available
refresh thread pool to use scaling with default size of 10
move cleaning filter cache on closed readers to separate thread
improve cleaning the global weighted cache when a reader closes, move it to a separate thread, so iterating over the cache entries will nto happen on each segment closed, but instead be "bulked"
Upgrade to netty 3.5.8
closes #2299.
provide the timer for netty
this helps to control the thread name of the thread it created
fix segments per tier to the proper 10 default
1.7 compiler failure
fixes #2294.
increase the clean interval of filter cache
add additional (internal) flush option
this flush option allows to just commit and index writer, without actually clearing the translog
If types and index mappings are empty consider the mapping as an "empty" mapping and return status 200.
formatting
add logging on the size of message received
Terms filter: Add `or` and `or_nocache` execution modes
closes #2306
close parser when parsing update body
simplify cleaning up non allocation shard code
its pretty complex today, simplify it by doing a single iteration, and handling both dangling shard cleanup on existing indices and shards that have been reallocated to a differetn node
Mapping: Using _default_ mapping type with _source excludes (or array based config) can cause the array to grow indefinitely
closes #2317
upgrade to jackson 2.1.0
improve allocation decision to allow to explain why a decision has been made
building the infra to support explaining why an allocation decision has been made, for example, why a shard is not allocated on a specific node