Docs: md -> asciidoc
Java API: fixed warnings in TermVectorRequest, also called super.validate for index not null check
Docs: Made config comment about min_master_nodes more explicit

Closes #2818
Java API: add index, type and id to ExplainResponse

Index, type and id were returned as part of the REST explain api response, but not through java api. That info was read out of the request, relying on the fact that the index would get overridden with the concrete one within that same request.

Closes #7201
Update clearcache.asciidoc

Changed `field_data` to `fielddata` to be consistent with the indices stats output

Closes #2888
vary offset/length (i hope) in compressed stream test