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
In order to make sure, that only the requested data is returned to the client,
a couple of fixes have been applied in the ClusterState.toXContent() method.
Also some tests were added to the yaml test suite
Closes#4885
Files were generated with the `thor api:generate:spec --force --verbose --crawl` command,
and based on the 0.90 branch (elasticsearch/elasticsearch@5ec4064).
Alexander Reelsen
Zachary Tong
Clinton Gormley
Spencer Alger
Igor Motov
Karel Minarik