Optimize dynamic mapping updates on master by processing latest one per index/node
Instead of processing all the bulk of update mappings we have per index/node, we can only update the last ordered one out of those (cause they are incremented on the node/index level). This will improve the processing time of an index that have large updates of mappings.
closes #4373
update the test to use the same API as 0.90
so backports will be simpler for now
Fixed local option explanation in TESTING readme
Add an `usage` key to the CPU section of OsStats.toXContent.

 This is just the sum of existing `sys` and `user`

Closes #4374
Update percolator highlighting docs.
Query String caching could cause matched_filters not working

When searching with a query containing query_strings inside a bool query, the specified _name is randomly missing from the results due to caching.

Closes #4361.
Closes #4371.
- fixing update mapping tests for index operations so the number of request will be based on the index thread pool size
- added update mapping tests for bulk operations
add node and order to the source of update mapping
Add generic assertion to all aggs.bucket tests to check if all shards were successful
Move Thread.sleep test to awaitBusy
Added refCount assertion due to LUCENE-5362
Beef up test to use more threads and iterations randomly
Enable Trace Logging for SearchWhileRelocatingTests
Support 'yaml' as a format for the Analyze API

Fixes #4311