Doc fix explaining resynchronization with the Cancel command.

Added line explaining resync process to Reroute/Cancel command.

Closes #5025
Merge pull request #5055 from seang-es/fix/5025

Doc fix explaining resynchronization with the Cancel command.
[DOCS] Add GridFS repository community plugin
[TEST] Removed nested quantifier in cat.allocation regex and made node name regex more liberal
Fixed parsing time zones as numeric value in DateHistogramParser

Closes #5057
Bulk process of shard started/failed should not execute on already processed events
closes #5061
add version and master_node flags to cluster state
[TEST] Fixed delete/50_refresh REST test to work against multiple nodes

delete/50_refresh tests per shard refresh using refresh:true in delete api. We might run into troubles though if we have a replica that gets initialized after a doc was indexed and deleted, without a refresh, as that doc won't be found when searching against that specific replica shard (as a refresh happens automatically before a replica gets exposed as started).
[DOCS] Added a table with 0.90/1.0 compatibility and corresponding instructions
[TEST] Add basic test for /cat/shards/{index}

Basic REST test for rendering the cat/shards endpoint.
[TEST] Fixed get_source/60_realtime_refresh REST test to work against multiple nodes

Replaced also wait for yellow with wait for green when using no replicas.

get_source/60_realtime_refresh tests per shard refresh using refresh:true and realtime:true in get api. We might run into troubles though if we have a replica that gets initialized after a doc was indexed without a refresh, as that doc will be found when searching against that specific replica shard (as a refresh happens automatically before a replica gets exposed as started).
[TEST] moved routing REST tests to 0 replicas

REST tests get run against either 1 node or multiple nodes. Wait for yellow with replicas>0 is not enough when running against multiple nodes as replicas shard might get initialized  during testing, which can cause timing issues.
[TEST] Added REST tests for _cat/thread_pool endpoint
[TEST] fixed typo in _cat/thread_pool docs
more AbstractRestResponseActionListener in RestThreadPoolAction (cat api)
[TEST] Made cat.count REST test more readable
Fix AndDocIdSet#IteratorBasedIterator to not violate initial doc state

AndDocIdSet#IteratorBasedIterator was potentially initialized with
NO_MORE_DOCS which violates the initial state of DocIdSetIterator and
could lead to undefined behavior when used in a search context.

Closes #5049