Templates for the beat config files have been updated to allow more
configuration options to be passed through to the associated
Elasticsearch index templates. In particular, one can optionally
specify values of index_template_max_docvalue_search to be set at
the creation of the beat index template. This can prevent shard failure
errors when viewing output in Kibana relating to "Trying to retrieve
too many docvalue_fields". Any similar config options can in future
be passed into the template via the elastic_beat_settings object.
Change-Id: Ic9136c8e063bbd231ed280bb446661b251879407