The `has_child` query's inner query now is wrapped in a filtered query with the child type as filter, this prevents other children from being returned as hit.
Extended the specialized simplified mapping source method to support metadata mapping fields. These fields can just specified as normal fields, but will automatically be placed as top level mapping field.

Closes #3818
move tests to unit test
enable delimited payload token filter

closes #3859
fix bug in term vector api, payloads were not handled correctly when some where missing

The array holding the payloads (TermVectorFields.payloads) is reused for each token. If the
previous token had payloads but the current token had not, then the payloads of the previous
token were returned, because the payloads of the previous token were never invalidated.
For example, for a field only contained two tokens each occurring once, the first having a
payload and the second not, then for the second token, the payload of the first was returned.

closes #3873
[DOCS] Add doc for delimited payload token filter
Add match query support for stacked tokens

SynonymFilters produces token streams with stacked tokens such that
conjunction queries need to be parsed in a special way such that the
stacked tokens are added as an innner disjuncition.

Closes #3881
[DOCS] Note that cutoff_frequency doesn't handle stacked tokens gracefully
Disable testSegmentsWithMergeFlag with AwaitsFix
index another doc in test and flush to force merge
Replaced hardcoded boolean value with correct parameter

Implemented changes suggested by review.

Closes #3898
fix naming in function_score

    - "boost" should be "boost_factor"
    - "mult" should be "multiply"

Also, store combine function names in ImmutableMap instead of iterating
over all possible names each time.

closes #3872 for master
Reenable test after fix
improve escaping of user paths

remove usage of if and () blocks as they clashed with user paths containing ()
postpone quotation of variables to prevent double escaping ("")
fix #3906

(cherry picked from commit 1cc095ec32a5b623f88c312f497ac5469887be97)
removed a duplicate paragraphin config docs
Added `num_queries` and `memory_size` stats to percolate stats.

Closes #3883
[DOCS] Added script.disable_dynamic to the scripting page
[DOCS] Added compound_on_flush docs and updated compound_format
docs to include note about accepting a float