Cluster State API: Remove index template filtering

The possibility of filtering for index templates in the cluster state API
had been introduced before there was a dedicated index templates API. This
commit removes this support from the cluster state API, as it was not really
clean, requiring you to specify the metadata and the index templates.

Closes #4954
Analyze API: Default analyzer accidentally removed stopwords

The analyze API used the standard analyzer from lucene and therefore removed
stopwords instead of using the elasticsearch default analyzer.

Closes #5974
Remove operation threading from broadcast actions
Similar to search removal, the operation threading options are not really ued, and the default should always be used. This also considerably simplifies the code.
A side affect is that we can now remove the ShardIterator#firstOrNull method, which can cause for sneaky bugs to occur.
closes #6044
[REST] Missing scroll id now returns 404

A bad/non-existing scroll ID used to return a 200, however a 404 might be more useful.
Also, this PR returns the right Exception (SearchContextMissingException) in the Java API.

Additionally: Added StatusToXContent interface and RestStatusToXContentListener listener, so
the appropriate RestStatus can be returned

Closes #5729
Added char_filters param to indices.analyze spec
[DOCS] Changed score_type to score_mode for has_child/parent queries