[Benchmark] Make TermsAggregationSearchBenchmark fairer to uninverted field data.

The benchmark indexes 200 unique full-width longs. For uninverted field data
we try to use the most memory-efficient storage, and in that case it would use
two arrays: one for the doc->ordinals mapping and one for the ordinal->value
mapping. Which is slower than what doc values do by storing directly the
mapping from docs to values.
Internal: expose the indices names every action relates to if applicable

Added two new interfaces:
1) IndicesRequest that allows to retrieve the indices the request relates to in a generic manner, together with the indices options that tell how they are going to get resolved and expanded
2) CompositeIndicesRequest for compound requests that hold multiple indices request like MultiSearchRequest, MultiGetRequest, MultiTermVectorsRequest, BulkRequest, BenchmarkRequest, PercolateRequest, MultiPercolateRequest and MoreLikeThisRequest

Taken the chance to streamline the indices options and add them to every request where it makes sense (although they can't be changed from the outside), rather than leaving them implicit in the related TransportAction when indices get expanded (tipycally MetaData#concreteIndices or MetaData#concreteSingleIndex). Added IndicesOptions parameter to MetaData#concreteSingleIndex to make sure it is taken from the request, where the information belongs, instead of hardcoded within MetaData. The concreteSingleIndex method remains but it's just a utility method that returns a single index instead of an array and complains otherwise.

Also made sure NPE is never thrown when setting indices(null) to IndicesAliasesRequest, similar to what SearchRequest does.

Closes #6933
remove use of recycled set in filters eviction
closes #7012
[TESTS] Ensure yellow in SimpleFacetsTests.testFilterFacetWithFacetFilterPostMode.
Aggregations: Added pre and post offset to histogram aggregation

Added preOffset and postOffset parameters to the API for the histogram aggregation which work in the same way as in the date histogram

Closes #6605
Add `wait_if_ongoing` option to _flush requests

This commit adds the ability to force blocking on the flush operaition
to make sure all files have been written and synced to disk. Without
this option a flush might be executing at the same time causing the
current flush to fail and return before all files being synced.

Closes #6996
Geo: Fixes parse error with complex shapes

The bug reproduces when the point under test for the placement of the hole of the polygon has an x coordinate which only intersects with the ends of edges in the main polygon. The previous code threw out these cases as not relevant but an intersect at 1.0 of the distance from the start to the end of an edge is just as valid as an intersect at any other point along the edge.  The fix corrects this and adds a test.

Closes #5773
Core: Use the provided cluster state instead of fetching a new cluster state from cluster service.

Close #7013
Add a periodic cleanup thread for IndexFieldCache caches

Fixes #7010