The example output for node info and cluster stats was outdated w.r.t.
to the information that is shown for plugins. With this commit we
updated the example output and update the explanation of the respective
fields.
The mem section was buggy in cluster stats and removed. It is now added back with the same structure as in node stats, containing total memory, available memory, used memory and percentages. All the values are the sum of all the nodes across the cluster (or at least the ones that we were able to get the values from).
The cluster stats api now returns counts for each node role. The `master_data`, `master_only`, `data_only` and `client` fields have been removed from the response in favour of `master`, `data`, `ingest` and `coordinating_only`. The same node can have multiple roles, hence contribute to multiple roles counts. Every node is implicitly a coordinating node, so whenever a node has no explicit roles, it will be counted as coordinating only.
we currently don't expose this.
This adds the following to the OS section of `_nodes`:
```
"os": {
"name": "Mac OS X",
...
}
```
and the following to the OS section of `_cluster/stats`:
```
"os": {
...
"names": [
{
"name": "Mac OS X",
"count": 1
}
],
...
},
```
Closes#11807
Also changes the response format of that section to:
```
"open_file_descriptors": {
"min": 200,
"max": 346,
"avg": 273
}
```
Closes#4681
Note: this is an aggregate of 3 commits in the 0.90 branch
