[docs] explain default settings for parameters of decay functions

relates to #8624
[Docs] Fix missing new line
[Docs] fix consistency between examples
[TEST] Reduce possible number of indices in the test - 10 indices can create tons of shards
MLT Query: Fix exclude with artificial documents

Artificial documents get assigned a random id. When include is set to false
(default), the ids of these documents also get included, when they should
rather be ignored.

Closes #8679
[TEST] Use different index on each iteration to ensure less timeout prone tests
Test: add trace logging to RelocationTests

also improved error message when failing to delete a dummy doc
[TEST] Add an assert for null indices in InternalEngineIntegrationTest
[TEST] remove outdated TestLogging annotation

Conflicts:
	src/test/java/org/elasticsearch/bwcompat/UnicastBackwardsCompatibilityTest.java
	src/test/java/org/elasticsearch/recovery/RelocationTests.java
[TEST] move test to a different class that can disable publish timeout on demand
[TEST] add back accidetially removed test logging
[TEST] With pipelining disabled requests can come back in any order

Closes #8697
function_score: match only document with score above custom score threshold

functon_score matched each document regardless of the computed score.
This commit adds a query parameter `min_score` (-Float.MAX_VALUE default).
Documents that have a score lower than this threshold will not be mached.

closes #6952
Docs: Additional info about _score calculation

Description taken from http://www.elasticsearch.org/guide/en/elasticsearch/guide/current/multi-query-strings.html / 110_Multi_Field_Search/05_Multiple_query_strings.asciidoc

Closes #8635
MLT Query: Support for ignore docs

Adds a `ignore_like` parameter to the MLT Query, which simply tells the
algorithm to skip all the terms from the given documents. This could be useful
in order to better guide nearest neighbor search by telling the algorithm to
never explore the space spanned by the given `ignore_like` docs. In essence we
are interested about the characteristic of a given item, but not of the ones
provided by `ignore_like`, thereby forcing the algorithm to go deeper in its
selection of terms. Note that this is different than simply performing a must
not boolean query on the unliked items. The syntax is exactly the same as the
`like` parameter.

Closes #8674
[TEST] Relax constraints of breaker tests even more

They were very stringent, and add values in worst-case situations. The
new values are acceptable while still testing the functionality of the
breaker.
[TEST] Explicit wait for fielddata breaker to be cleared
Update daterange-aggregation.asciidoc

Clarified the date-math expressions on date range aggregations

Closes #8703
Logging - provides template usage information on index creation
Closes #7421
[TEST] Try to speed up REST tests by reducing max number of replicas and shards