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
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
Core: fix index throttling to notice a change to max_merge_count on the next merge start/finish

Previously such changes were never noticed, and index throttling kept
kicking in at the original setting from startup.

Closes #8136

Closes #8132
Docs: Added 'd' to the list of supported units.

Day was missing from the list of supported units in the date math section.

Closes #8151
Update plugins.asciidoc

Added Vietnamese Analyser to plugins page

Closes #6647
Parent/child: Reduce memory usage in top children query.

Closes #8165
Closes #8160
Docs: Update minimum-should-match.asciidoc

Add %-sign to examle in the last section

Closes #8157
Docs: Update filtered-query.asciidoc

Fix mistyping

Closes #8167
Docs: Provide example of deleting a repository

Example of deleting a repository with explanation that snapshots themselves are left untouched.

Closes #8172
Docs: missing quote

fix missing quote

Closes #8176
Parent/child: Check if there is a search context, otherwise throw a query parse exception.

Also added a bwc test that runs a delete by query with a has_child query and verifies that only that operation is ignored when recovering from disk during a upgrade.

Closes #8031
Closes #8177