[DOCS] More assertive statement about requiring `query` in _count, etc
fixed the reduce of InternalGeoHashGrid when executing on a single shard
Added more unit like test that verifies that has_child is never cached even if wrapped by another filter.
Throw exception if `cluster.name` is specified in TestCluster node settings

We rely on the `cluster.name` setting to be the same across all nodes
and transport clients etc. If a node setting contains `cluster.name`
the test might not work if a random transport client is swapped
in. Passing such a configuration should result in an exception since
it's clearly an illegal state.
Use different field names based on the data type in aggregations tests.

Tests fail once in a while because of a ClassCastException at the mvel level.
We suspect that this happens because a script that is JIT-ed on a specific
data type cannot later be used with another one, but we didn't manage to
reproduce in our development environments, so let's try to change the field
names to see if this error keeps occurring.
Re-Sort config/names
Removed old serialization logic (<= 1.0-RC1) in readFrom and writeTo methods.
Removed duplicated registration of warmers as custom metadata type

Already done in a static block within IndexMetaData
Removed put/delete warmer tests that were meant to test that the serialization was bw compatible after adding support for acks
Removed redundant version checks in transport serialization (#4731 leftover)
Remove duplicate cache columns
Normalize cat headers, add aliases

Closes #4852.
Add tera and peta to RestTable.renderValue()

Closes #4871
Install SecurityManager inside ElasticsearchTestCase for easier randomization

We currently run always with SecurityManager installed. To make sure we
work also without we should randomly swap it out ie. run without the
security manager.
_cat/allocation: Guaranteed to have at least zero shards
_cat/allocation: disk.avail can be zero, if so, want to show 100%

Closes #4835
[DOCS] Updated the breaking changes for the fields param

Closes #4888
Don't throttle the translog stage of recovery
After copying the index files (which are throttled), we currently throttle the translog as well. The translog phase3 part is performed under a lock, so its better not to throttle it at all, and move it as fast as possible.
Fix test to use at least one document
mget REST API should support source parameter

As stated in documentation, we should support `?source=` parameter in mget REST operations.

This is how to reproduce it:

```sh
curl -XDELETE "http://localhost:9200/test"

curl -XPOST "http://localhost:9200/test/type/1?refresh" -d'{
    "foo": "bar"
}'

curl -XPOST "http://localhost:9200/test/type/_mget" -d'{
    "ids": ["1"]
}'

curl -XGET "http://localhost:9200/test/type/_mget?source=%7B%22ids%22%3A%20%5B%221%22%5D%7D"
```

Closes #4892.