[Tests] testNodeVersionIsUpdated stopped but didn't close it's node
[TEST] use more verbose assertion in IndicesRequestTests
[TEST] Agg may not be a instance of StringTerms, but UnmappedTerms, so use common Terms class instead
Nested: If the `_type` field isn't indexed nested docs must be filtered out.
[DOCS] Document NOT as a simple_query_string flag

Fixes #7426
Test: Fixed pluggable transport module test to support transportclient

Also made sure, that only a change of requests is tested for and not
an initial value, which might not be set in case of a node client.
Tests: Improve test coverage.

Close #7428
Context suggester: infinite loop in GeolocationContextMapping

Close #7433
[TESTS] Temporarily disable FileBasedMappingsTests.
document field parsing: refactor to remove external value mechanism

The external value mechanism was a workaround for not beeing able to set
a value while parsing a field value. It was used for example by geo point
to set the values for the lat and lon field. However, its the major
disadvantage was that it made the code hard to read.
This commit removes the external value from parse context and instead
adds a new method FieldMapper.addValue() which can be used to add fields
to a mapper that are unrelated to the currently parsed source.
In addition, this method is now used also by the multi_field handling so that
parsing is called only once and the parsed value (or any other) is passed
to multi_fields explicitely. Before, multi_fields relied on the parser
being at a particular position.
This means that now values which are objects or arrays in a json structure
can also be passed to multi_fields which was not possible before
(see BaseTypeMapperTests where all test except for testMultiFieldsWithArray
failed without this change).