This allows specifying the path an index will be at.
`index.data_path` is specified in the settings when creating an index,
and can not be dynamically changed.
An example request would look like:
POST /myindex
{
"settings": {
"number_of_shards": 2,
"data_path": "/tmp/myindex"
}
}
And would put data in /tmp/myindex/0/index/0 and /tmp/myindex/0/index/1
Since this can be used to write data to arbitrary locations on disk, it
requires enabling the `node.enable_custom_paths` setting in
elasticsearch.yml on all nodes.
We only have a single gatweway since es 1.3. There is no need to keep all
these abstractsion and nested packages. We can fold most of it into simpler
structures.
