Add debug logging to help diagnose intermittent upgrade test failures.

Also fixed indentation in ElasticsearchMergePolicy.
Update cat.nodes regex

Support for multi-word node names like 'Henry "Hank" McCoy'
Snapshot/Restore: fix snapshot of a single closed index

Snapshot of a closed index can leave snapshot hanging in initializing state.

Fixes #8046
Docs: add the predefined language-specific stopword lists to stop-tokenfilter.asciidoc
Docs: adds note about using null_value with dynamic templates

Closes #7874
Docs: Adding community-contributed Scout plugins

Scout plugins for reporting key node, cluster, and index health metrics.

Closes #7937
Docs: Fix order for PUT _mapping docs

Closes #8083
Docs: Added RethinkDB River to list of community plugins

Closes #8016
Docs: Update query-string-query.asciidoc

Update sample

Closes #8024
Docs: fix typo

Closes #8111
Docs: Typo: s/by/be/

Closes #8114
Improve amibiguous ES_HEAP_SIZE warning in deb init script

Closes #3554
More improvements to debug logging for upgrade test.
Remove unnecessary log level setting in upgrade test.
Fixing copy/paste mistake in SearchRequest.extraSource's exception message.
Docs: Documented the http.*host and transport.*host settings
Docs: Update id-field.asciidoc

It is strange to provide an example with `"store" : false` when talking about possibility of enabling the field to be stored.
Broke the line in the mapping in two lines for better readability.
More verbose sentence above the mapping.

Closes #7894
Docs: Some Data Cant't be obtained.

In previous case, the first 100 data can't be obtained.

Closes #8103
Docs: Percolate `_score` reference

Added missing `_score` word, made the sentence less ambiguous.

Closes #8115
Docs: Percolate reference - a typo and a misused word

Closes #8116