[TEST] UnicastBackwardsCompatibilityTest should not copy internal node settings to external nodes

Recent test failures triggered by #7289 were caused by this, simply because internal node settings (transport type key) that are not supported by the external older nodes were copied to them by mistake.
Internal: adjusted internal requests visibility from public to package private
opened up getting the template name from DeleteIndexTemplateRequest
Geo: fixes circle radius calculation

This change fixes the creation circle shapes o it calculates it correctly instead of essentially using the diameter as the radius.  The radius has to be converted into degrees but calculating the ratio of the desired radius to the circumference of the earth and then multiplying it by 360 (number of degrees around the earths circumference).  This issue here was that it was only multiplied by 180 making the result out by a factor of 2.  Also made the test for circles actually check to make sure it has the correct centre and radius.

Closes #7301
Warmer (search) to support query cache
allow for search based warmer to support query cache flag on the search request, and use the index level query caching flag if set.
closes #7326
Aggregations: Scriptable Metrics Aggregation

A metrics aggregation which runs specified scripts at the init, collect, combine, and reduce phases

Closes #5923
fix to compile issue caused by scripted metric aggregation change
Internal: make sure that all shard level requests hold the original indices

A request that relates to indices (`IndicesRequest` or `CompositeIndicesRequest`) might be converted to some other internal request(s) (e.g. shard level request) that get distributed over the cluster. Those requests contain the concrete index they refer to, but it is not known which indices (or aliases or expressions) the original request related to.

This commit makes sure that the original indices are available as part of the shard level requests and makes them implement `IndicesRequest` as well.

Also every internal request should be created passing in the original request, so that the original headers, together with the eventual original indices and options, get copied to it. Corrected some places where this information was lost.

NOTE: As for the bulk api and other multi items api (e.g. multi_get), their shard level requests won't keep around the whole set of original indices, but only the ones that related to the bulk items sent to each shard, the important bit is that we keep the original names though, not only the concrete ones.

Closes #7319
Internal: adjusted internal requests visibility from public to package private (redo)

was just reverted by mistake in the failed attempt of isolating the change and taking it out of #7319
NPE in ShardStats when routing entry is not set yet on IndexShard
closes #7356
Query Cache: Add hit and miss count
closes #7355
[TEST] Improve robustness of restoreIndexWithMissingShards test
Term vector API: return 'found: false' for docs between index and refresh

Closes #7121
Aggregations: Remove the logic to optionally sort/dedup values on the fly.

These options are not used anymore. Instead numeric values can now contain dups
and it is the responsibility of the aggregation to deal with it (eg. terms).
And otherwise all values sources are now sorted, which is the contract of the
interfaces that they implement.

Close #7276
Facets: Removal from master.

Close #7337
[TEST] fixed concurrency issue in IndicesRequestTests
[TEST] bw comp testMultiGet should wait for yellow, not for green
Internal: Remove CacheRecycler.

The main consumer of this API was the faceting module. Now that it's gone,
let's remove CacheRecycler as well.

Close #7366
[PARSER] Clarify XContentParser/Builder interface for binary vs. utf8 values

Today we have very confusing naming since some methods names claim to
read binary but in fact read utf-16 and convert to utf-8 under the hood.
This commit clarifies the interfaces and adds additional documentation.

Closes #7367
More Like This Query: Switch to using the multi-termvectors API

The term vector API can now generate term vectors on the fly, if the terms are
not already stored in the index. This commit exploits this new functionality
for the MLT query. Now the terms are directly retrieved using multi-
termvectors API, instead of generating them from the texts retrieved using the
multi-get API.

Closes #7014