Set shards and replicas settings for index creation

[ghost]

Hi,

This PR is intended to give the option to set shards and replicas for the elastalert index creation, this could be useful in environments with one elasticsearch node.

Best Regards

[eht16]

For anyone interested, here is an updated diff: https://gist.github.com/eht16/135e3e3e21d5a0506a909febf574fd07

I think this would be a useful addition. For example, my use case is also a one-node ES cluster so I don't need replicas and for rather small indices I prefer only one or two shards.

@mjflve would you mind updating the PR?

[admlko]

I agree, this would be nice to have. In my case, there is no need for extra 4 primary shards taking up resources.

@eht16 Cheers for the diff :)

[karlskewes]

Be great to get this merged in. Thanks for putting it together.

[benetis]

Any reason why this wasn't merged?

[mmguero]

I've created a new updated diff based on the one @eht16 created on Mar 21, 2018.

If interested, it's here.