Plugin does not respect server.basePath

We get 404 errors, because it's never included in the query path. It also seems to ignore the port and goes with 80. We're still considering whether we'll be using Elasticsearch+Kibana or something else, but this bug took us a day to figure-out that it's not our fault that the queries don't work.

The issue names no files, tests, or entry points. Trace how the plugin constructs Elasticsearch query URLs and reads server.basePath and the server port; confirm the fix by checking that requests include both values and no longer return 404 errors.

Written by the indexing model from the issue text.