Add 'version' mapping type

[fredeil]

Add attribute mapping and Fluent mapping for the version type (see https://www.elastic.co/guide/en/elasticsearch/reference/master/version.html)

Additional context
See this issue elastic/elasticsearch#48878, elastic/elasticsearch#62692 and elastic/elasticsearch#59786.

[stevejgordon]

Thanks for raising this @fredeil. This is also included in the items in #5096 and is in my list to pick up after the next piece of work with a view to getting it into the next release. I'll close this as we're tracking in the meta ticket.