[TEST] don't use multiple names (e.g. aliases) pointing to the same concrete index when using indexRandom

indexRandom will try to delete bogus documents multiple times since they get tracked by indexOrAlias/id, and after the actual deletion any other attempt throws error and fails the test
plugins: `bin` and `config` only plugins do not install correctly

When installing a bin only plugin, it is identified as a site plugin.

A current workaround would be to create in the zip file another empty dir. So if you have:

* `bin/myfile.sh`
* `empty/empty.txt`

the `bin` content will be extracted as expected.

Closes #7152.
[Test] fix plugins: `bin` and `config` only plugins do not install correctly

Related to #7152.
Query DSL: Cache range filter on date field by default

A range filter on a date field with a numeric `from`/`to` value is **not** cached by default:

    DELETE /test

    PUT /test/t/1
    {
      "date": "2014-01-01"
    }

    GET /_validate/query?explain
    {
      "query": {
        "filtered": {
          "filter": {
            "range": {
              "date": {
                "from": 0
              }
            }
          }
        }
      }
    }

Returns:

    "explanation": "ConstantScore(no_cache(date:[0 TO *]))"

This patch fixes as well not caching `from`/`to` when using `now` value not rounded.
Previously, a query like:

    GET /_validate/query?explain
    {
      "query": {
        "filtered": {
          "filter": {
            "range": {
              "date": {
                "from": "now"
                "to": "now/d+1"
              }
            }
          }
        }
      }
    }

was cached.

Also, this patch does not cache anymore `now` even if the user asked for caching it.
As it won't be cached at all by definition.

Added as well tests for all possible combinations.

Closes #7114.
Test: Allow CliTool to write out stacktraces

In order to have the possibility of debugging on the command line, the user
now can either set the es.cli.debug system property
which results in stack traces being written to to the terminal.

Closes #7222