Test: force merge index in the end of IndexStatsTests.throttleStats

This works around slow IO (fsync) causing the test-framework cleanup
to timeout at 30 seconds when trying to delete the index.

Closes #8528
[TEST] Register data.path for all nodes on close in InternalTestCluster

We need to register those data paths otherwise we might miss path that
need to get cleaned when using local gatway etc. which can otherwise
cause imports of dangeling indices.

Conflicts:
	src/test/java/org/elasticsearch/test/InternalTestCluster.java
[TEST] Give tests for ctx._ttl more leeway

Fixes #8500
[TEST] set log level to trace for action.search
Docs: Update execution hint docs for Significant terms agg

copied over the relevant pieces from the terms agg

Closes #8532
Test: don't enable unnecessary http transport in restoreIndexWithShardsMissingInLocalGateway test
Logging: restrict files loaded as logging configuration based on their suffix

Make sure that files such as logging.yml.rpmnew or logging.yml.bak are not loaded as logging configuration.

Only files that start with the "logging." prefix and end with ".yaml", ".yml", ".json" and ".properties" suffix get loaded.

Closes #7457
[TEST] move LoggingConfigurationTests to common.logging.log4j

Make also LogConfigurator#ALLOWED_SUFFIXES package private so that it can be used in LoggingConfigurationTests, now that it's in the same package as the class that it tests.
Add few randomized aspects to LoggingConfigurationTests.
[DOCS] document that we support loading multiple logging conf files
Fix example in logging daily rotate configuration

PR #8464 come with a bug in the example provided.

First, the current log file is not compressed so it should not end with `.gz`.
Second, conversion pattern was removing all the log content but was printing only the log date.
Then, the current log filename was hardcoded to `elasticsearch` instead of the cluster name.

(cherry picked from commit cbced94)
Fix: If dangling_timeout was set to 0 and auto_import_dangled
was set to yes, dangling indices were deleted by mistake,
because a RemoveDanglingIndices runnable was added
to every dangling indices, without considering the auto_import_dangled
setting.
[GEO] Add LinearRing and LineString validity checks as defined by http://geojson.org/geojson-spec.html to ensure valid polygons are specified at parse time.

Closes #8433
fixed NPE in LocalGatewayMetaState
[CORE] Ban all useage of Future#cancel(true)

Interrupting a thread while blocking on an NIO Read / Write Operation
can cause a file to be closed due to the interrupts. This can have unpredictable
effects when files are open by index readers etc. we should prevent interruptions
across the board if possible.

Closes #8494

Conflicts:
	src/main/java/org/elasticsearch/gateway/local/state/meta/LocalGatewayMetaState.java
Internal: IndexService - synchronize close to prevent race condition with shard creation

During node shutdown we have a race condition between processing cluster state updates (creating shards) and closing down the index service. This may cause shards to leak and not be closed properly.

This commit removes the concurrency in shard closing as InternalIndexService.removeShard has been synchronized for a long time now.

On the other hand, the commit restores the parallel shutdown of indices lost in 7e1d8a6ca3b23c07cbaebe72831c7ef4a201bd2b

Closes #8557
[CORE] Free pending search contexts if index is closed

Today we hold on to search context reference if they are not cleaned
up for a while until a reaper thread trashes them if they timed out.
This commit removes all pending contexts once the index is closed to release
resources and filehandles immediatly once the index is closed.
Core: Added query/filter wrapper that builds the actual query to be executed on the last possible moment to aid with index aliases and percolator queries using `now` date expression.

Percolator queries and index alias filters are parsed once and reused as long as they exist on a node. If they contain time based range filters with a `now` expression then the alias filters and percolator queries are going to be incorrect from the moment these are constructed (depending on the date rounding).

 If a range filter or range query is constructed as part of adding a percolator query or a index alias filter then these get wrapped in special query or filter wrappers that defer the resolution of now at last possible moment as apposed during parse time. In the case of the range filter a special Resolvable Filter makes sure that `now` is resolved when the DocIdSet is pulled and in the case of the range query `now` is resolved at query rewrite time. Both occur at the time the range filter or query is used as apposed when the query or filter is constructed during parse time.

Closes #8474
Closes #8534
[TEST] Add search trace logging for debugging
Revert "[CORE] Free pending search contexts if index is closed"

This reverts commit ad48563d31181ecd1e649a549a541b383018e8ff.
Revert "[TEST] Add search trace logging for debugging"

This reverts commit a1ea09f43efcc3e211ad3833297af6d86610f6df.