#61 and #62 renamed settings by deprecating old ones and creating new ones.
In version 3.0.0, we can remove old settings.

That said, we should not remove it from master doc before 2.6.0 is released.

Closes #70.

Claim issue 23570

With this commit we reduce usage of two time-consuming methods on the hot code
path: generating random numbers and determining the current timestamp. This also
changes behavior slightly:

* The `hostname` field will vary host names from 1 - 3 in a regular pattern
instead of randomly (however, as the host name is e.g. `web-EU-1.elastic.co` and
only the number changes non-randomly we deem this change ok)
* The `offset` will change be more realistic now: Before it changed randomly and
now the offset increases by the average event size up to a certain maximum.
* The current `@timestamp` will be retrieved only once per bulk. For documents
within a bulk we'll advance the microsecond portion by `1 / bulk size`
microseconds.

We've measured the performance impact of this change by stubbing out
Elasticsearch with nginx and running the `index-logs-fixed-daily-volume`
challenge with the following track parameters:

* `bulk_size`: 20000
* `bulk_indexing_clients`: 16
* `number_of_days`: 1
* `daily_logging_volume`: "20GB"

We have measured the following median indexing throughput in our test
environment:

* baseline (master): 153476 docs/s
* Using a deterministic `hostname` and `offset`: 174371 docs/s
* All three measures together: 222611 docs/s

This means we improve the maximum achievable indexing throughput by 45% in this
configuration.

fix elastic#70 elastic#125

…lastic#70)

Ability to increase the EBS disk size on terraform created stacks

* This commit is for https://engageli.atlassian.net/browse/MPC-1457,
and the JIRA has a confluence page linked that provides additional
information.

It adds the capability to increase the EBS disk size on
terraform created stacks for these instance roles:
* EMS
* Engageli
* Merger
* Recorder

Here is the required variables in the tfvars to enable this
feature, and the values are in Gb.  The value of `8` is the
default, so adding this section as is, will not make any
changes to the instances:

```
ebs_root_volume_size = {
  "engageli" = 8
  "ems" = 8
  "merger" = 8
  "recorder" = 8
}
```

For the variables it uses the new map format, since the existing
map has been deprecated:
  https://www.terraform.io/docs/language/functions/map.html
modified:   aws/ams-cluster-v1-tf/ems.tf
modified:   aws/ams-cluster-v1-tf/main.tf
modified:   aws/ams-cluster-v1-tf/variables.tf

Approved-by: Gideon Avida

With this commit we update the Rally config file template so it does not
include any JDK references. With elastic/rally#518 we will resolve JDK
versions using the `JAVAx_HOME` environment variables.

Relates elastic/rally#518
Closes elastic#70
Relates elastic#71