update readme

fix empty objects being normalized as arrays

update to PHP 8 & ES 8

# Conflicts:
#	composer.json

# Conflicts:
#	composer.json

* bump development version number

* missing support

added missing support to [field value factor](https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-function-score-query.html#function-field-value-factor)

* updated docs

* proposed changes

Merge branch '2019-06-27-daterangeaggregation' of https://github.com/pmishev/ElasticsearchDSL into pmishev-2019-06-27-daterangeaggregation

# Conflicts:
#	src/Aggregation/Bucketing/DateRangeAggregation.php

* master branch dev versions set to 6.1-dev

* introducing field aware trait and named builder interface

* Adding param `track_total_hits` (#273)

* Add getQuery Method to FunctionScoreQuery (#271)

* Add getQuery Method to FunctionScoreQuery

Add getQuery Method to FunctionScoreQuery in order to apply changes to query of FunctionScoreQuery.

* Update FunctionScoreQuery.php

* added new NestedSort for replacing deprecated nested_filter and nested_path (#267)

* added new NestedSort for replacing deprecated nested_filter and nested_path

* made the filter optional

* remove keyed option condition for to have range key

* update readme version matrix

* fix php psr2 style issues in the FunctionScore class

* Initialize static serializer on wakeup

# Conflicts:
#	src/FieldAwareTrait.php
#	src/Sort/NestedSort.php

From the Elasticsearch documentation:

If no fields are provided, the multi_match query defaults to the
`index.query.default_field` index settings, which in turn defaults to
`*`. `*` extracts all fields in the mapping that are eligible to term
queries and filters the metadata fields. All extracted fields are then
combined to build a query.